UC-NRLF 


ABORATORY  STUDIES 


ELEMENTARY  CHEMISTRY 


COOLEY 


^^i^&simism 


RICAN   BOOK   COMPANY 
CINCINNATI 'CHICAGO 


-Summer  Cohool  Of  Ghoaipt'yy  • 

LIBRARY 

OF   THE 

UNIVERSITY  OF  CALIFORNIA. 


Received 
Accession  No. 


LABORATORY  STUDIES 


IN 


ELEMENTABY  CHEMISTEY 


BY 

LsKOY    C.    COOLEY,   PH.D. 

PROFESSOR  OF   PHYSICS  AMD  CHEMISTRY    IN   VASSAR  COLLEGE 


UNIVERSITY 


NEW  YORK     •:•     CINCINNATI     •:•     CHICAGO 

AMERICAN  BOOK   COMPANY 


COPYRIGHT,  1S94,  HY 

AN    BOOK.    COMPANV. 


COOLEY  LAB.  STUD. 


UITI7BRSIT7 


PREFACE. 


I  KNOW  of  only  one  way  to  make  the  study  of  elementary 
chemistry  useful  in  education,  and  that  is  to  fix  the  mind 
of  the  student  habitually  on  things  and  events  brought 
under  his  own  eye  in  such  a  way  that  he  shall  be  impelled 
to  learn  the  properties  and  actions  of  substances  by  his  own 
observations.  Laboratory  work  is  indispensable  for 'this 
purpose. 

But  a  student  cannot  learn  by  observation  what  he  has 
already  been  told  by  a  teacher  or  a  text-book.  To  enable 
him  to  learn  facts  by  personal  observation,  rather  than  to 
verify  the  statements  of  facts  found  in  books,  should  be 
the  aim  of  laboratory  work. 

If  rightly  directed,  the  laboratory  method  of  study  in 
elementary  chemistry  is  adapted  to  cultivate  mental  powers 
and  habits  of  the  greatest  value.  Among  these  we  may 
specially  notice  the  following;  viz., — 

The  habit  of  making  exhaustive  observations,  and  the 
power  to  give  clear  and  accurate  descriptions. 

The  habit  of  collecting  the  facts  pertaining  to  a  subject, 
the  ability  to  compare  them  and  to  classify  them,  and 
the  power  to  draw  logical  inferences  from  them  and  to 
make  correct  generalizations. 


4  PREFACE. 

In  order  to  secure  these  results,  no  desultory  or  hap- 
hazard work  should  be  tolerated  in  the  laboratory. 

Every  experiment  should  be  undertaken  with  a  well- 
defined  object  in  view.  Every  step  in  the  work  should  be 
taken  in  accordance  with  a  deliberately  formed  plan. 

The  beginner  will  need  the  help  of  the  most  specific 
directions  for  work,  and  considerable  prompting  toward  the 
observation  of  results.  He  will  also  need  sympathetic 
encouragement  to  describe  what  he  actually  sees,  and  con- 
stant attention,  lest  he  record  his  observation  in  bad  form. 

On  the  other  hand,  his  mind  should  not  be  prejudiced 
by  foreknowledge  of  the  facts  which  the  experiments  are 
competent  to  reveal,  for  the  beginner  finds  it  very  difficult 
not  to  see  that  which  he  knows  ought  to  be  seen.  That 
his  observations  may  be  genuine,  he  should  not  be  sub- 
jected to  the  temptation  or  unconscious  tendency  to  twist 
the  statement  of  what  is  actually  seen  into  the  statement 
of  what  the  text-book  says  should  appear.  This  may  be 
avoided  by  giving  very  specific  directions  for  the  work,  so 
that  the  right  conditions  shall  be  secured  in  the  experiment, 
and  then  leaving  the  results  to  be  detected  by  the  student, 
and  stated  in  his  own  words.  The  laboratory  guide  and 
the  general  text-book  should  therefore  be  separate  volumes. 

But  experimental  work  is  not  all  there  should  be  in  the 
school  or  college  course ;  along  with  the  specific  discipline 
of  such  work  there  should  be  the  broadening  influence  of  a 
text-book,  or  course  of  lectures.  The  laboratory  and  the 
classroom  should  work  hand  in  hand. 


PREFACE.  5 

The  following  course  of  laboratory  studies  is  constructed 
in  accordance  with  the  foregoing  views  of  what  should  be 
the  aims  of  experimental  chemistry  in  the  general  educa- 
tional work  of  the  schools. 

A  wise  selection  of  laboratory  studies  devoted  to  funda- 
mental facts  and  principles  will  furnish  satisfactory  mate- 
rials for  use  in  connection  with  any  course  in  elementary 
general  chemistry  which  the  teacher  may  choose  to  use. 
The  number  of  experiments  may  be  larger  than  are  needed ; 
the  order  in  which  they  are  placed  may  not  be  the  order 
chosen  for  the  discussion  of  the  subjects  to  which  they 
relate ;  but  the  independent  teacher  will  find  that  their 
value  is  not  lessened  by  the  need  of  selection. 

I  believe  that  the  subjects  treated  in  this  book  are  such 
as  should  be  chosen  for  the  purpose  stated.  I  am  quite 
sure  that  the  order  in  which  they  are  given  is  a  logical 
order,  but  I  believe  that  it  is  not  the  only  one.  I  would 
leave  the  teacher,  who  desires  to  do  so,  quite  free  to  map 
out  the  lecture  or  text-book  course  for  himself,  but  would 
furnish  a  stock  of  materials  which  may  be  drawn  upon  for 
the  laboratory  part  of  it,  in  any  course,  provided  only  that 
it  is  devoted  to  elementary  general  chemistry. 

In  conclusion  I  may  gratefully  add  that  I  am  indebted  to 
Miss  E.  M.  FREEMAN  and  to  PROFESSOR  C.  W.  MOULTON 

for  valuable  suggestions  in  regard  to  details  in  several  of 

the  "  Studies  "  in  this  course. 

L.  C.  C. 

VASSAR  COLLEGE,  January,  1894. 


SUGGESTIONS   TO   THE   STUDENT. 


IN  REGARD  TO  THE  WORK.  —  In  each  study  proceed  in 
the  following  order  :  — 

1.  Notice   the    object  fcof   the   experiment,  and  read  the 
directions  for  the  work  which  is  to  accomplish  it. 

2.  Arrange  the  apparatus  and  use  it  exactly  as  directed. 
Do   not   attempt    modifications    until    your    experience    in 
manipulation  is  large  enough  to  warrant  your  doing  so. 

3.  Watch  intently  for  every  change  that  takes  place,  and 
note  accurately  every  important  change  as  soon  as  it  has 
occurred. 

4.  Study  the  results  thoughtfully  in  order  to  detect  their 
meaning  and  discover  what  they  teach. 

5.  Compare  the  results  with  others  which  you  may  have 
obtained  with  other  substances  under  similar  conditions,  and 
try  to  discover  the  differences  and  the  resemblances  of  the 
properties  and  actions  of  the  substances  involved. 

Ix  REGARD  TO  NOTES.  —  The  notebook  should  be  always 
at  hand,  and  you  should  heroically  insist  on  making  the 
notes  of  your  experiment  at  the  time,  while  the  experiment 
is  going  on. 

Notes  should  be  the  original  record  of  the  work  :  no  copies 
of  them  should  be  offered  to,  or  accepted  by,  the  instructor. 

7 


8  SUGGESTIONS   TO   THE  STUDENT. 

After  they  have  been  examined  by  the  instructor,  and  the 
corrections  made,  they  may  be  copied  into  your  blank  book 
for  preservation,  and  used  for  reference  and  reviews. 
In  the  notes  on  every  experiment  you  should  — 

1.  Briefly   describe   the   apparatus   and    materials    used, 
their  arrangement  and  the  work  done  with  them.     A  simple 
sketch  of  the  apparatus  is  very  useful. 

2.  Briefly  describe  all  the  changes  that  occur  during  the 
operations. 

3.  Briefly  state  the  conclusions  tlrawn,  or  give  an  explana- 
tion of  the  changes,  and  show  what  the  experiment  teaches. 


CONTENTS. 


PART  I. 
Chemistry  of  Nonmetals. 

SECTION.  PAGE. 

I.   CHEMICAL  CHANGES 11 

II.   PREPARATION  AND  STUDY  OF  GASES 20 

To  Liberate  and  Collect  a  Gas 20 

Study  of  Oxygen 23 

Study  of  Hydrogen 2(3 

III.  ACIDS,  BASES,  AND  SAT/PS 29 

IV.  DEFINITE  PROPORTIONS 34 

V.    WATER 37 

VI.    HYDROCHLORIC-ACID  AND  OTHER  CHLORIDES    ...  43 

VII.    THE  CHLORINE  GROUP 46 

VIII.    SULPHUR  AND  SOME  OF  ITS  COMPOUNDS 50 

Sulphur  and  the  Sulphides 50 

Sulphuric  Acid  and  Sulphates 53 

Sulphur  Dioxide  and  Sulphites 54 

Comparison  of  Sulphides,  Sulphites,  and  Sulphates    .  56 

IX.    NITROGEN 58 

X.    ANALYSIS  OF  Ant 60 

XL   AMMONIA:    THE    COMPOUND  OF   NITROGEN  AND   HY- 
DROGEN       65 

XII.    NITRIC  ACID,  NITROGEN  OXIDES,  NITRATES      ...  69 

XIII.  CARBON,  CARBON  DIOXIDE,  CARBONATES      ....  74 

XIV.  COMBUSTION      ...  79 


PART  II. 

Reactions  and  Properties  of  some  Compounds  of  Metals, 
and  Exercises  in  tabulating  Results. 

SECTION.  PAOE. 

I.   POTASSIUM,  SODIUM,  AMMONIUM 82 

II.   CALCIUM,  BARIUM,  STRONTIUM 87 

III.   MAGNESIUM  90 


10  CONTENTS. 

SECTION.  PAGE. 

IV.   ZINC 91 

Y.    CADMIUM 94 

VI.   MERCURY ,     ...  96 

VII.   SILVER 99 

VIII.    COPPER 101 

IX.    LEAD 104 

X.   TIN 108 

XI.    ARSENIC,  ANTIMONY,  BISMUTH Ill 

XII.    ALUMINUM        114 

XIII.  CHROMIUM 1K5 

XIV.  MANGANESE 120 

XV.    IRON 123 

XVI.    NICKEL,  COBALT  .  127 


PART  III. 

Application    of   Certain    Foregoing   Reactions  to 
Qualitative    Analysis. 

SECTION.  PAGE. 

I.    PRELIMINARY  STATEMENTS 130 

II.   THE  ANALYTICAL  CLASSIFICATION 130 

III.  THE  ANALYTICAL  GROUPS 131 

IV.  ANALYSIS  OK  A  SIMPLE  SALT 132 

To  find  what  Metal  the  Salt  contains 132 

To  find  what  Acid  Radical  the  Salt  contains  ....  134 

Hints  in  regard  to  Notes 134 

V.   ANALYSIS   OF    A   COMPLEX   SUBSTANCE                   .     .  135 


APPENDIX. 

A.  TABLE  OF  THE  ELEMENTS 137 

B.  THE  METRIC  MEASURES 138 

C.  APPARATUS  AND  CHEMICALS    .  .     .  139 


it*  VKX 

TT! 


PART  I. 

CHEMISTRY  OP  NONMETALS. 


I.     CHEMICAL   CHANGES. 


EXPERIMENT  1. 
Object.  —  To  ascertain  the  effect  of  heating  magnesium. 

Manipulation.  —  Obtain  a  piece  of  magnesium  wire  or 
ribbon  about  six  inches  long ;  grasp  one  end  of  it  with 
pincers,  and  hold  the  other  end  for  a  few  moments  in  the 
name  of  the  Bunsen  lamp  and  then  over  a  sheet  of  paper 
on  the  table  while  the  change  goes  on. 

Notes.  —  Describe  the  work,  as  you  did  it,  briefly  in  your 
own  words.  Describe  all  the  changes  you  can  discover. 
Note  particularly  whether  the  substance  of  the  wire  or 
ribbon  is  changed. 

EXPERIMENT  2. 
Object.  —  To  ascertain  the  effect  of  heating  iron. 

Manipulation.  —  Use  a  piece  of  iron  wire,  and  proceed 
to  heat  it  as  you  heated  the  magnesium  in  Exp.  1. 

Notes.  —  Briefly  describe  the  work  in  your  own  words. 
Describe  all  the  changes  you  can  discover.  Note  particu- 
larly whether  the  substance  of  the  wire  is  changed. 

General.  —  In  the  foregoing  experiments  you  should 
discover  the  marked  difference  in  magnesium  and  iron  with 
respect  to  the  changes  produced  by  heat  in  the  nature  of 
these  substances.  The  change  witnessed  in  magnesium  is 

11 


12 


LABORATORY  STUDIES  IN   CHEMISTRY. 


typical  of  one  kind  of  changes  in  bodies  generally,  known 
as  chemical  changes;  while  those  seen  in  the  iron  are 
typical  of  the  other  kind,  known  as  physical  changes. 


Fig.    1. 


EXPERIMENT   3. 

Object.  —  To  ascertain  the  effect  of  heat  on  mercuric  oxide, 
and  to  distinguish  the  physical  from  the  chemical 
changes. 

Manipulation.  —  Put  1  g.  of  mercuric  oxide  into  a  side- 
neck  ignition  tube x  (Fig.  1).  Close  the  mouth  of  the  tube 
with  a  tightly  fitting  cork,  and  slip  one  end  of  a 

piece  of  rubber 
tubing  (e,  Fig. 
2)  over  the  end 
of  the  side  neck, 
and  the  other 
over  the  end  of 
a  glass  tube  long 
enough  to  reach 
the  bottom  of  the  test  tube, 
as  shown.  Fix  the  side- 
neck  tube  obliquely  in  a 
clamp  of  the  retort  stand 
/.  Put  3  cc.  of  water  into  the  test  tube  b,  and  the  glass 
delivery  tube  into  it. 

Apply  the  flame  of  a  lamp,  and  move  it  slowly  to  heat  the 
glass  gradually  and  evenly,  remembering  that  the  upper 
part  of  the  tube  should  not  be  heated  (discover  why  farther 

1  The  tube  must  be  clean  and  dry.  A  piece  of  dry  cloth,  or  a 
sponge  tied  on  the  end  of  a  wire  or  stick,  is  convenient  for  wiping 
tubes.  Ignition  tubes  are  made  of  "hard"  glass,  while  other  tubes 
are  made  of  "soft"  glass.  Hard  glass  will  stand  a  strong  heat, 
while  soft  glass  will  not.  Common  test  tubes  may  be  used  for  heat- 
ing liquids;  ignition  tubes  should  be  used  for  heating  dry  solids. 


Fig.  2. 


CHEMICAL   CHANGES.  13 

on).  Watch  for  and  note  the  changes  as  they  occur.  While 
bubbles  are  escaping  rapidly  in  b,  light  a  long  splinter  of 
wood ;  extinguish  the  flame ;  thrust  the  glowing  end  down 
into  the  tube. 

Notes.  —  Describe  all  the  changes.  Note  particularly 
every  evidence  of  the  production  of  two  new  substances, 
and  of  the  loss  of  the  mercuric  oxide. 

End  the  Experiment.  —  When  the  action  has  nearly 
ceased,  or  at  any  time  you  may  wish  to  stop  it,  remove  the 
glass  tube  from  the  water  in  b  ;  lower  the  gas  flame  to  cool 
the  ignition  tube  gradually.  When  the  ignition  tube  can 
be  handled,  place  it  erect,  and  put  the  glowing  end  of  a 
splinter  into  it.  Try  it  again. 

Notes.  —  Describe  all  changes  which  occur  while  the 
tube  is  cooling.  Consider  what  substances  have  been 
brought  out  of  the  oxide  by  the  heat.1  What  physical 
changes  in  the  oxide  occurred  ?  What  chemical  changes  ? 
Why  should  the  upper  end  of  the  ignition  tube  be  kept 
cold  in  this  experiment  ?  Why  should  the  ignition  tube 
be  cooled  gradually  ? 

EXPERIMENT  4. 

Object.  —  To  ascertain  the  physical  and  chemical  effects  of 
heat  on  potassium  chlorate. 

Manipulation.  —  Grind   2   g.  of   potassium   chlorate  in 
a  mortar  (Fig.  3).      Transfer  it  to  a  dry 
ignition  tube,   arrange   the  apparatus   as 
shown  in  Fig.  2,   and   proceed   to    study 
the  effects  of  heat  as  directed  in  Exp.  3. 

When  the  glowing  end  of  the  splinter 
shows  that  the  air  has  been  all  driven  out 

rig.   o. 

of  tube  b,  transfer  the  delivery  tube  e  over 

1  Oxygen  is  a  colorless  gas  which  intensifies  combustion.  Mer- 
cury is  a  lustrous,  silver-colored,  liquid  metal. 


14  LABORATORY  STUDIES   IN   CHEMISTRY. 

into  test  tube  c.  Two  or  three  test  tubes  may  be  filled 
with  the  gas  in  this  way.  Each  one  should  be  immediately 
closed  with  a  cork. 

Notes.  —  Describe  all  the  changes  seen  in  the  chlorate. 
Note  particularly  every  evidence  of  the  production  of  new 
substances.  Name  that  found  in  the  test  tubes.  What 
physical  changes  did  the  heat  produce  in  the  chlorate  ? 
What  chemical  changes  ? 

EXPERIMENT  5. 

Object.  —  To  study  the  effect  of  oxygen  on  red-hot  charcoal. 

Manipulation.  —  Wind  the  end  of  a  small  wire  around 
a  little  splinter  of  charcoal.  Heat  the  tip  of  the  charcoal 
until  it  glows ;  then  lower  it  into  the  gas  in  the  test  tube  c 
(Fig.  2).  Pour  a  little  strong  limewater  into  c;  close  the 
tube  and  shake  it  briskly.  Add  limewater  to  tube  b  ;  close 
it  and  shake  briskly. 

Notes.  —  Describe  the  action  of  oxygen  on  the  hot  char- 
coal ;  also  the  change  in  the  limewater  in  c.  Judge  by  the 
limewater  in  b  whether  the  effect  in  c  is  caused  by  oxygen. 
How  can  you  account  for  the  change  in  the  limewater  ?  1 
Where  now  are  the  oxygen  and  the  carbon  (charcoal)  which 
were  used  up  in  the  action  ? 

EXPERIMENT  6. 

Object.  —  To   study   the   changes  produced  by  the   mutual 
action  of  the  vapors  of  ammonia  and  Jiydrochloric  acid. 

Manipulation.  —  Put  about  1  cc.  of  ammonia  water  into 
a  tube  or  bottle  ;  rinse  the  walls  with  it,  and  pour  the 
excess  away.  Put  as  much  hydrochloric  acid  into  another 
similar  vessel,  and  treat  it  in  the  same  way.  By  this  means 

1  Carbon  dioxide  is  a  colorless  gas  which  whitens  limewater. 


CHEMICAL   CHAGtS.  15 


the  vessels  are  filled  with  the  colorless-,  vapors  of  the  two 
substances.    Bring  the  two  vessels  mouth  to  mouth, 
and  hold  them  one  above  the  other  (Fig.  4). 

Notes.  —  Describe  the  chemical  change.     How 
can  you  account  for  the  new  substance  ? 

General.  —  The  change  witnessed  in  Exps.  3  and 
4  were  alike  in  this  respect  ;  a  single  substance  dis- 
appeared, while  two  others  were  obtained.     These 
changes  typify  a  large  class  of  chemical  changes, 
called  decomposition.     The  changes  in  Exps.  5  and 
6  were   alike,    but   in    marked   contrast  with    the    Fj    4 
others  in  this  respect  :  two  substances  disappeared, 
while  one  only  was  obtained.     These  changes  are  typical 
of  another  class  of  chemical  changes,  called  combination. 

EXPERIMENT  7. 
Object.  —  To   study  the  changes  produced   by  the   mutual 

action  of  zinc  and  dilute  sulphuric  acid. 
Manipulation  and  Notes.1  —  Into  a  wide-mouthed  bottle 
which  can  hold  about  200  cc.  put  about  50  cc.  of  water, 
and  add,  little  by  little,  8  cc.  of  strong  sulphuric  acid,  shak- 
ing the  bottle  meantime  to  mix  the  liquids.  Note  an  im- 
portant effect.2  Drop  fragments  of  zinc,  about  10  g.,  into 
the  dilute  acid,  and  cover  the  bottle  with  a  square  of  glass 
or  of  heavy  paper  (note).8  Lift  the  cover,  and  at  the  same 

1  Since  results  should  be  described  as  soon  as  they  are  seen,  you 
will  find  henceforth  the  hints  for  notes  given  with  the  directions  for 
manipulation. 

2  This  effect  becomes  dangerously  great  when  water  is  poured  into 
the  acid.     This  should  never  be   done.     Whenever  strong  sul- 
phuric acid  and  water  are  to  be  mixed,  always  pour  the  acid  grad- 
ually into  the  water  while  you  stir  it. 

3  The  word  note  will  henceforth  indicate  that  you  should  here 
discover  results  of  special  value,  and  describe  them  in  your  notes. 


16  LABORATORY  STUDIES  IN   CHEMISTRY. 

moment  bring  a  match  flame  to  the  mouth  of  the  bottle 
(note).  Let  the  action  go  on  until  the  effervescence  (escape 
of  gas  bubbles)  is  quite  or  nearly  ended.  There  may  be  a 
residue  of  zinc  and  also  a  black  sediment  in  the  liquid. 
This  sediment  is  the  impurity  of  the  zinc  which  has  dis- 
appeared. Can  you  detect  any  change  in  the  dilute  acid  ? 
It  may,  nevertheless,  contain  some  new  substance  in  solution. 
To  Search  for  a  Product  in  Solution.  —  The  liquid 
must  be  rid  of  any  sediment.  To  obtain  it  clear,  it  should 
be  filtered  ;  and  then,  to  obtain  any  solid  it  may  be  holding 
in  solution,  it  may  be  evaporated. 

1.  Filtration.  —  Cut  a  square  of  filter  paper  (A,  Fig.  5), 

the  length  of  one  side  being 
a  little  less  than  twice  the 
length  of  the  sloping  side 
of  a  funnel,  I).  Fold  the 
square  into  a  triangle  by 
bringing  corners  d  and  a  to- 
gether. Fold  again,  bring- 
ing corners  c  and  b  together, 
Fig.  5.  making  the  triangle  B.  Trim 

the   edges   along  a  circular 

line,  e  B  h.  Open  the  triangle  (leaving  three  thicknesses  of 
paper  on  one  side,  and  one  on  the  other),  and  you  will  have 
a  little  paper  funnel,  (7,  which  will  fit  neatly  in  the  glass 
funnel  D.  Press  it  into  D  and  wet  it  with  water.  Then 
rest  D  on  a  test  tube  and  pour  the  liquid  into  it.  The  clear 
liquid  which  should  run  through  it  is  called  a,  filtrate. 

2.  Evaporation.  —  Pour  the  clear  liquid  into  an  evapo- 
rating dish  and  heat  it  over  a  low  flame,  as  shown  in  Fig.  G. 
Evaporation  is  not  boiling.     To  evaporate  a  liquid,  you  may 
heat  it  until  it  begins  to  simmer,  but  should  not  agitate 
it  by  violent  ebullition.     This  caution  is  especially  needed 
when  the  volume  of  the  liquid  is  small,    and   absolutely 


CHEMICAL    CHANGES. 


17 


Fig.  6. 


necessary  when  no  loss  must  be  incurred.  Evaporate  this 
liquid  until  a  drop,  when  cooled  on  a  glass  rod  or  plate,  will 
yield  a  solid.  Then  let  the  liquid  cool. 

Describe  the  result,  and  compare  any 
solid  product  with  the  substances  used. 
How  many  and  what  are  the  products  of 
the  mutual  action  of  zinc  and  sulphuric 
acid  ? 1 

Compare  the  number  of  substances 
used  with  the  number  of  new  ones 
obtained,  and  judge  whether  the 
chemical  change  is  a  simple  decom- 
position, or  a  direct  combination,  or 
neither. 

EXPERIMENT  8. 

Object.  —  To  study   the  changes  produced   by  the  mutual 

action  of  sodium  chloride  and  silver  nitrate  in  solution. 
Manipulation  and  Notes.  —  Drop  a  small  crystal  of 
silver  nitrate  into  a  test  tube  containing  5  cc.  of  water,  and 
shake  it  until  it  is  dissolved.  In  another  tube  dissolve  a 
little  sodium  chloride  (common  salt).  Add  a  drop  or  two 
of  the  chloride  to  the  nitrate  (note).  Go  on  adding  the 
solution  of  the  chloride  carefully,  drop  by  drop,  shaking 
the  tube  vigorously  after  each  addition,  and  letting  the 
upper  layer  of  the  liquid  become  clear  enough  to  let  you  see 
whether  the  next  drop  makes  any  change.  Do  this  until  a 
drop  makes  no  change,  and  then  stir  the  liquid  with  a  glass 
rod  wet  with  the  silver-nitrate  solution.  Your  liquid  can 
now  contain  almost  none  at  all  of  either  silver  nitrate  or 
sodium  chloride  unchanged. 

1  Hydrogen  is  a  colorless  gas  which  takes   fire  with  explosion. 
Zinc  sulphate  is  a  solid  which  dissolves  in  water,  but  reappears,  or 
evaporation,  in  the  form  of  slender,  colorless  crystals. 
2 


18  LABORATORY    STUDIES   IN   CHEMISTRY. 

Filter  the  mixture.  Describe  the  precipitate  (the  solid 
left  on  the  filter)  when  it  is  fresh,  and  again  after  it  has 
been  exposed  to  sunlight. 

Evaporate  the  filtrate  until  little  is  left,  and  then  let  it 
cool  quietly  (note). 

What  are  the  products  of  the  mutual  action  of  silver 
nitrate  and  sodium  chloride?  l  Judge  whether  the  change 
is  simple  decomposition,  or  direct  combination,  or  neither. 
Also  see  whether  you  can  find  any  difference  between  this 
case  and  that  in  Exp.  7. 

EXPERIMENT  9. 

Object.  —  To  study  the  cheat  ye  produced  by  the  mutual  ac- 
tion of  mercuric  chloride  and  potassium  iodide  in  solution. 

Manipulation  and  Notes.  —  Use  enough  mercuric  chlo- 
ride, in  powder,  to  halfway  fill  the  rounded  part  of  the  bottom 
of  a  test  tube.  Cover  it  with  about  5  cc.  of  water,  and  warm 
it  until  it  is  dissolved.  Put  about  twice  as  much  potas- 
sium iodide  into  another  tube,  and  dissolve  it  also  in  water. 
Pour  about  150  cc.  of  water  into  a  wide-mouthed  bottle,  and 
add  the  solution  of  mercuric  chloride.  Next  add  about  half 
of  the  solution  of  potassium  iodide  little  by  little  (note). 

Go  on  adding  the  iodide  carefully,  noticing  whether  more 
of  the  new  substance  is  made  by  each  addition ;  and,  that 
you  need  make  no  mistake,  wait  each  time  until  the  liquid 
clears  before  you  add  the  next  drop.  Do  this  until  the  last 
drop  yields  no  change ;  then  stir  the  liquid  with  a  glass  rod 
wret  with  mercuric  chloride  (give  reason)? 

1  Silver  chloride  is,  when  freshly  made,  easily  darkened  hy  ex- 
posure to  light;  and  when  dry,  a  white  powder.     Sodium  nitrate  is  a 
solid,  soluble  in  water,  from  which  it  crystallizes  by  evaporation. 

2  The  words  give  reason  or  explain  will  henceforth  be  used  to  ask 
you  to  give  a  reason  for,  or  make  an  explanatory  statement  in  regard 
to,  whatever  subject  is  immediately  before  it.     In  this  case  it  means, 

Why  stir  with  a  glass  rod  wet  with  mercuric  chloride  ? 


CHEMICAL    CHANGES.  19 

Filter  the  mixture  and  evaporate  the  filtrate  (note).  What 
are  the  products  of  the  changes  in  this  experiment  ?  1  Are 
the  changes  examples  of  simple  decomposition,  or  of  direct 
combination  ?  Can  you  decide  whether  they  are  like  those 
found  in  Exp.  7,  or  those  in  Exp.  8  ? 

EXPERIMENT  1O. 

Object.  —  To  study  the  action  of  iron  and  sulphur  in  the 
cold,  and  when  heated. 

Manipulation  and  Notes. — Mix  1.5  g.  of  the  finest 
iron  filings  with  .84  g.  of  flowers  of  sulphur  very  inti- 
mately in  a  mortar.  Look  at  a  little  of  this  substance 
with  a  strong  magnifying  glass,  to  see  if  you  can  detect 
the  grains  of  iron  and  of  sulphur  (note).  Judge  whether 
any  chemical  change  has  occurred. 

Transfer  the  substance  to  an  iron  spoon,  or  an  ignition 
tube,  and  heat  it  intensely,  even  to  redness  if  necessary 
(note).  Pulverize  the  product  in  a  mortar,  examine  it 
closely,  and  judge  whether  a  chemical  change  has  occurred. 

General.  —  Substances  intimately  mingled  together,  but 
retaining  their  properties,  constitute  a  mixture.  If  sub- 
stances lose  their  identity  by  mutual  action  when  brought 
together,  the  product  is  a  chemical  compound. 

1  Mercuric  iodide  is  a  scarlet  solid,  insoluble  in  water.  Potassium 
chloride  is  a  white  solid,  soluble  in  water. 


LABORATORY    STUDIES    IN    CHEMISTRY. 


II.     PREPARATION   AND   STUDY   OF   GASES. 


Fig.  7. 


I.     To  Liberate  and  Collect  a  Gas. 

1.    Collecting  by  Displacement  of  Air.  —  Use  a  set  of  flasks 

or  bottles  fitted  up  as  shown  in  Figs.  7  and  8.  A  conical 

flask  is  provided  with  a  soft- 
rubber  stopper  with  two  holes. 
Through  each  hole  there  passes 
a  glass  tube  bent  at  right  an- 
gles, —  one  with  a  long  branch 
to  reach  almost  to  the  bottom 
of  the  flask,  the  other  only  long 
enough  to  reach  through  the 

stopper.     You  can  easily  cut  these  tubes  to  proper  length 

with  a  triangular 

file,  and  bend  them 

when  softened  by 

a    Bunsen    flame. 

As  many  of  these 

collecting  flasks  as 

you  may  need  can 

be  joined  in  series, 

as  shown  in  Fig.  8, 

—the  long  tube  of 

a  with  the  tube  of 

the  side-neck  gen- 

.erator,     and     the 

long  tube  of  each  one  following  with  the  short  tube  of  the 

one  before  it.     The  ends  of  the  glass  tubes  are  joined  by 


Fig.  8. 


PREPARATION  AND    STUDY    OF    GASES. 


21 


Fig.  9. 


short  pieces  of  rubber  (r,  r),  and  should  meet  inside  these 
connections.  From  the  last  flask  a  rubber  tube  may  reach 
over  into  water  in  an  open  bottle,  e.  m 

The  gas  may  be  "washed"  by  bubbling 
through  water  in  a  ;  and  another  advantage 
of  this  water,  and  that  in  e  also,  is  this  : 
you  can  see  by  the  bubbles  whether  the  gas 
is  coming  off  rapidly  or  slowly,  and  can 
regulate  the  heat  accordingly. 

All  the  flasks  must  be  closed  air-tight.  Rubber  stoppers 
easily  make  air-tight  joints.1 

Instead  of  the  "  all-glass  connection"  just  described,  "  rub- 
ber-tube connec- 
tion "  may  be 
used,  as  shown 
in  Fig.  10.  The 
stopper  of  each 
flask  is  provided 
with  straight 
glass  tubes,  as  in 
Fig.  9,  and  the 
flasks  are  -con- 
nected by  pieces 
of  rubber  tubing 
six  or  eight 
inches  long.  The  apparatus  is  more  quickly  and  easily  set 
up  in  this  way,  at  first ;  but  glass  is  more  reliable  than  rub- 
ber for  conveying  gases,  and  the  set,  once  prepared  with 
glass,  can  be  as  quickly  put  together  afterward  as  the  other. 
All  joints  should  be  tested,  and  proved  to  be  air-tight,  by 
trying  to  force  the  breath  through  them. 

1  A  set  once  fitted  up  is  a  sort  of  general  gas  works  for  the  labora- 
tory table;  for,  as  we  shall  see,  most  gases  may  be  collected  in  this 
way.  To  collect  gases  lighter  than  air,  the  flasks  should  be  joined 
with  their  short  tubes  toward  the  generator. 


LABORATORY    STUDIES    IN    CHEMISTRY. 


Fig.  11. 


2.  Collecting  by  Displacement  of  Water.  —  The  gas  is  led 
from  the  generator  (g,  Fig.  11)  by  a  delivery  tube  (t)  of 

glass  or  rub- 
ber, to  the 
mouth  of  a 
bottle,  cyl- 
inder, or 
flask,  previ- 
ously filled 
with  water 
and  invert- 
ed in  a  wa- 
ter pan  or 
cistern  (B). 
A  piece  of 
smooth  tile 

or  marble,  or  some  equivalent,  about  2\  inches  square  and  \ 
inch  thick,  for  the  bottle  to  stand  on,  with  the  mouth  pro- 
jecting over  its  edge,  is  desirable,  although  one  can  do 
without  it,  as  shown  in  the  cut. 

Small  bottles  or  tubes  may  be  filled  with  water  by  simple 
immersion  in  the  pan,  but  the  water  must  not  be  deep ;  hence 
proceed  as  follows.  Fill  the  bottle  to  the  brim  with  water. 
Cut  a  piece  of  paper  a  little  larger  than  its  mouth ;  slide 
it  on  as  a  cover,  and  smooth  it  down  closely  upon  the  glass 
(Fig.  11,  a).  Grasp  the  bottle,  and  turn  it  bottom  upward 
over  the  pan ;  lower  it  into  the  water ;  remove  the  paper, 
and  leave  the  bottle  standing  in  the  water.  The  pressure  of 
the  atmosphere  will  safely  hold  the  water  in  the  bottle 
while  you  invert  it,  and  while  its  mouth  is  under  water. 

3.  Collecting  by  Use  of  both  Methods  at  once.  —  Put  the 
water  pan  B  (Fig.  11)  in  place  of  the  bottle  e  (Fig.  8). 

The  Generator.  —  The  materials  from  which  the  gas  is 
to  be  set  free  may  be  put  into  (a)  a  side-neck  flask  (Fig.  8) 


PREPARATION  AND   STUDY   OF  GASES. 


Fig.  12. 


or  a  side-neck  tube  (Fig.  10)  ;  or  (b)  a  common  flask,  with 
stopper  and  bent  glass  delivery  tube  (Fig.  12).     Or  (c)  in 
case  no  heat  is  to  be  applied,  a  bottle 
generator    (Fig.    13)     is    very    satisfac- 
tory.    Select  a  bottle  whose 

capacity  is  300  to  500  cc., 

the  mouth  of  which  is  2.5 

to   3   cm.    inside    diameter. 

Fit  a  sound  cork  or  a  rubber 

stopper  with  two  tubes, — 

one  a  bent  delivery  tube  (b), 

the  other  a  "  thistle  tube  " 

.(£),  which  reaches  nearly  to 

the    bottom    of   the    bottle. 

Through  this  tube  liquid  can 
is.  be  Poure<l  at  pleasure,  while  no  gas  can  escape, 

because  the  lower  end  is  closed  by  the  liquid. 
(d)  The  thistle  tube  may  be  used  with  any  of  the  preceding 
forms  of  generator,  if  desired. 

II.     Study  of  Oxygen. 

Oxygen  may  be  obtained  by  heating  mercuric  oxide 
(Exp.  3)  or  potassium  chlorate  (Exp.  4).  The  chlorate  is 
preferred ;  and  the  chlorate  will  yield  its  oxygen  more 
readily  when  mixed  with  manganese  dioxide. 

EXPERIMENT  11. 

Object.  —  To  liberate  oxygen  from  potassium  chlorate,  and  to 
discover  its  properties. 

1.     To  LIBERATE  AND  COLLECT  THE  GAS. 
Manipulation  and  Notes.  —  Take  6  g.   of  potassium 
chlorate  and  grind  it  to  powder  in  a  mortar.    Add  3  g.  of 
manganese  dioxide.      Mix  the  two  powders.     Put  the  mix- 


7BRSIT7 


24  LABORATORY  STUDIES  IN   CHEMISTRY, 

ture  into  a  side-neck  tube.  Cork  the  tube  tightly,  and  fix 
it  in  the  clamp,  as  shown  in  Fig.  10  (p.  21). 

Use  four  flasks  and  a  bottle,  with  glass  tubes  (Fig.  8, 
p.  20).  Leave  a  empty.  Cover  the  bottom  of  b  with  sand, 
and  add  water,  so  that  the  end  of  the  long  tube  shall  be 
just  below  the  surface.  Put  a  layer  of  water  in  the  bottle 
also.  Prove  the  joints  to  be  air-tight. 

Heat  the  mixture  in  the  generator,  at  first  with  a  low 
flame,  and  move  the  burner  so  as  to  heat  the  tube  uniformly 
.  (give  reason).  Gradually  turn  on  a  higher  flame,  and  let  it 
play  first  against  the  upper  part  of  the  mixture  (give  reason). 
If  at  any  time  the  gas  is  given  off  too  fast  (shown  by  the 
bubbles  in  the  water),  remove  the  flame  until  the  flow  is 
slackened.  Note  any  change  in  the  substances  used.  Ob- 
serve how  the  gas  drives  the  air  from  flask  to  flask,  and  out 
at  e. 

When  the  bottle  e  is  filled  with  O,1  as  you  may  learn 
by  means  of  a  glowing  splinter  put  just  witln  i  its  mouth, 
you  can  put  a  water  pan,  previously  made  reaJy,  in  place 
of  the  bottle  e,  covering  this  bottle  with  a  glass  plate,  and 
fill  two  or  three  bottles  with  gas  by  displacement  of  water 
(Fig.  II).2 

Disjoin  the  generator  from  a  by  taking  the  rubber  tube 
from  «,  and  lower  the  flame  to  cool  the  tube  slowly  (give 
reason).  Also  take  the  rubber  tube  from  the  short  tube  of 
the  last  flask. 

1  One  or  two  letters  are  often  written  instead  of  the  whole  name 
of  an  element.     Thus  O  stands  for  oxygen,  H  stands  for  hydrogen, 
and  Cl  stands  for  chlorine.     In  reading  and  speaking,  however,  use 
the  word:   say  "oxygen"  rather  than  "  O,"  etc.     These  abbrevia- 
tions are  called  symbols.     Every  element  has  a  symbol.     See  Table 
of  Elements,  Appendix,  A. 

2  Six  grams  of  the  chlorate  is  capable  of  yielding  about  1.5  liters 
of  O.     Some  will  be  lost  while  collecting  it  (give  reason),  so  that  the 
total  capacity  of  the  apparatus  use  1  should  not  much  exceed  1  liter. 


PREPARATION  AND   STUDY  OF  GASES.  25 


2.     To  DISCOVER  THE  PROPERTIES  OF  OXYGEN. 

Manipulation  and  Notes.  —  (a)  What  is  its  color  ? 
To  discover  its  odor,  test  the  gas  in  bottle  e  (note).  Leave 
the  bottle  uncovered. 

(b)  Is  it  lighter  or  heavier  than  air  ?     To  answer  this 
question,  find,  by  a  glowing  taper,  whether  the   gas   still 
remains  in  the  open  bottle  (note),  and  judge  how  the  result 
bears  on  the  question.     Slip  a  glass  plate  under  the  mouth 
of  a  bottle  which  was  filled  by  displacement  of  water ;  place 
the  bottle  on  the  table,  mouth  upward ;  uncover,  and  let  it 
stand  a  full  minute,  then  test  with  the  glowing  taper  (note). 
If  you  have  a  second  bottle  filled,  lift  it  from  the  water, 
mouth    downward,    and    hold   it    in   this    position    a   full 
minute ;  test  with  the  glowing  splinter  (note).     Show  how 
these  results  bear  on  the  question. 

(c)  What  is  the  effect  of  0  on  the  burning  of  a  candle  ? 
To  find  an  answer,  make  a  taper  test  (Fig.  14)  as  follows : 
Bend  a  wire  as  shown  ;  then  warm  the  lower  end, 

and  press  it  into  the  bottom  of  a  piece  of  one  of  the 
smallest  kind  of  wax  candles.  Light  the  taper,  and 
lower  the  flame  a  little  way  into  the  flask  c  (note). 
Extinguish  the  flame,  but  leave  a  glow  upon  the 
Wick  ;  lower  it  into  the  gas  (note).  After  the  burn- 
ing of  the  taper  in  the  gas,  pour  a  little  limewater 
into  the  flask  and  shake  it  well  (note).  Compare 
results  with  those  noted  in  Exp.  5,  and  explain.  Fig'  14' 

(d)  How    will    red-hot    iron    be    affected    by   oxygen  ? 
Take  a  piece  of  small  iron  wire  and  bind  about  one  third 
of  a  match  to  one  end.     Set  fire  to  the  match,  and  lower  it 
into  the  mouth  of  the  flask  b,  lowering  still  further  as  the 
action  goes  on  (note).     Be  careful  that  the  hot  wire  does 
not  touch  the  glass  (give  reason). 


26  LABORATORY  STUDIES   IN  CHEMISTRY. 

III.     Study  of  Hydrogen. 

EXPERIMENT  12. 

Object.  — To  liberate  hydrogen  from  dilute  sulphuric  acid, 
and  to  discover  its  properties. 

1.     To  LIBERATE  HYDROGEN  FROM  DILUTE  SULPHURIC 

ACID. 

Manipulation  and  Notes. — Put  the  materials  into  a 
side-neck  flask,  and  collect  the  gas  over  water  (Fig.  11, 
p.  22).  A  thistle  tube  is  desirable.  Refer  to  (c)  and  (d),  p.  23. 

To  60  cc.  of  water  in  a  beaker  add  slowly,  with  stirring, 
12  cc.  of  strong  sulphuric  acid.  Slide  fragments  of  zinc,  10 
or  12  g.  (it  should  not  be  dropped)  into  the  flask.  If  a 
thistle  tube  is  used,  insert  the  stopper  tightly.  Pour  the 
dilute  acid  through  the  thistle  tube  until  the  lower  end  is 
covered  (ffive  reason).  More  acid  may  be  added  as  needed 
to  keep  up  the  action.  If  no  thistle  tube  is  used,  pour  the 
whole  of  the  acid  upon  the  zinc  at  once,  and  quickly  close 
the  flask.  Do  not  use  the  first  bottlefid  collected  (give  reason), 
nor  the  second,  if  the  bottles  are  smaller  than  the  flask. 
After  filling  two  or  three  small  bottles  with  the  gas,  leaving 
them  standing  mouth  downward  in  the  water,  proceed  at 
once  to  discover  the  properties  of  the  gas. 

2.    To  DISCOVER  THE  PROPERTIES  OF  HYDROGEN. 

Manipulation  and  Notes (a)  What  is  its  color  and 

its  odor  ? 

(b)  Is  this  gas  heavier,  or  lighter,  than  air  ?  To  answer 
this  question,  fill  a  test  tube  by  displacement  of  water. 
Close  it  with  the  thumb.  Lift  it  from  the  water,  keeping 
its  mouth  downward.  Remove  the  thumb,  and  a  little 
while  afterward  bring  a  lighted  match  to  its  mouth.  Again 
proceed  with  another  tube  in  the  same  way,  except  that  you 
keep  its  mouth  upward  (note). 


PREPARATION  AND   STUDY  OF  GASES.  27 

(c)  To  study  the  "  explosibility  "  of  hydrogen,  fill  a  tube 
a  third  full  of  water,  and  displace  this  by  H.1  Consider 
what  the  tube  now  contains.  Close  it  with  the  thumb.  Lift 
it  from  the  water.  Hold  it  at  arm's  length,  with  its  mouth 
downward.  Remove  the  thumb,  and  at  the  same  moment 
present  the  match  flame  to  the  mouth  of  the  tube  (note). 

Fill  the  test  tube  full  of  water.  Displace  by  H.  Lift  it 
and  fire  it  as  you  did  the  one  before.  Compare  the  two 
results.  Try  to  give  a  reason  for  the  difference. 

Can  H  burn  without  exploding  ?  Try  it  with  an  appara- 
tus shown  in  Fig.  15.  Select  a  piece  of  glass  tubing  about 
the  size  of  the  stem  of  a  3-inch  funnel,  and  cut  from  it  a 
portion  about  4  inches  long.  Heat  the  middle  of  this,  con- 
stantly rolling  it  in  the  Bunsen  flame  until  it  softens,  and 
then  pull  it  lengthwise  with  both  hands,  and  thus  draw  it 
out  to  the  size  of  a  knitting  needle.  Cut  the  small  tube 
near  the  enlargement  at  one  end.  You  now  have  a  short 
tube  which  tapers  down  to  a  small  opening.  Fix  this  upon 
the  stem  of  the  funnel  by  a  short  rubber  connection. 

Select  an  evaporating  dish  large  enough 
to  let  the  funnel  stand  within  it  (a  mortar 
may  stand  more  firmly).  Put  enough  di- 
lute hydrochloric  acid  (half  water)  into  the 
dish  to  well  cover  the  edge  of  the  funnel. 
Drop  some  pieces  of  zinc  into  the  acid, 
and  stand  the  funnel  over  it  in  the  dish 
(Fig.  15).  When  the  air  has  been  all 
driven  out  (in  about  a  minute,  if  the  action  Flg-  15' 

is  brisk),  you  may  touch  a  splinter  flame  to  the  gas  jet,  at 
arm's  length. 

The  gas  must  come  off  steadily  and  freely.     More  zinc  or 
more  acid  may  be  put  under  the  funnel,  if  needed,  without 
letting  any  air  enter   around    its    mouth.      Xote  the  first 
1  See  note  1,  p.  24. 


28          LABORATORY  STUDIES  IN    CHEMISTRY. 

effect,  then  what  follows.     Try  to  explain  both,  and  point 
out  the  condition  in  which  H  is  explosive. 

(d)  What   is    the    product   of   burning    H  ?      Bring   the 
mouth  of  a  clean,  dry,  cold,  wide-mouthed  bottle  down  over 
the  flame  of  H  (Fig.  15)  for  a  few  moments   (note).     What 
do  you  infer  the  product  to  be  ?     Is  the  evidence  conclu- 
sive ? 

(e)  To  obtain  dry  H,  take  a  "  drying  tube  "  (a,  Fig.  16)  ; 
put  a  little  cotton  wool  into  the  bulb  loosely ;  fill  the  tube 

nearly  full  of  granulated 
calcium  chloride,1  and  put 
a  thin  layer  of  cotton 
over  it.  Next  close  the 
large  end  with  a  cork 
pierced  with  a  hole  to 
receive  the  stem  of  the 
funnel.  A  small  jet  tube 
may  be  joined  to  the  small 
end  of  this  tube  (b,  Fig. 
16). 

Put  zinc  into  the  dish. 
Place    the  funnel  in    the 
dish   over  it,   and  clamp 
the  drying  tube  as  shown. 
Fig-  16~  Pour  dilute  acid  into  the 

dish.     Make  the  action  steady  and  brisk. 

(/)  After  waiting  a  minute  or  two,  until  sure  that  the 
air  has  been  expelled,  set  fire  to  the  H  at  the  top  of  the 
jet,  and  then  hold  a  wide-mouthed  bottle,  which  is  clean 
and  dry,  over  the  flame,  as  shown  at  c.  What  is  now  pro- 
duced by  the  burning  of  H  ?  Which  is  the  more  conclusive 
experiment,  —  (d)  or  (/)  ?  Why  ? 

1  Calcium  chloride  absorbs  moisture  from  air  and  gases  very 
greedily. 


ACIDS,   BASES,   AND   SALTS.  29 


III.    ACIDS,  BASES,  AND   SALTS. 


EXPERIMENT   13. 

Object.  —  To  ascertain  some  characteristics  of  sulphuric  acid. 

Manipulation  and  Notes.  —  («)  What  is  its  taste  ? 1 
Try  it  in  this  way :  Add  a  drop  or  two  of  the  acid  to  a  test 
tube  nearly  full  of  water.  Mix  them  by  stirring  with  a 
glass  rod,  and  then  present  a  small  drop  011  the  end  of  the 
rod  to  the  tongue. 

(b)  How  does  it  affect  the  color  of  litmus  ?  To  answer 
this,  fill  a  bottle  two  thirds  full  of  water,  and  add  enough 
solution  of  blue  litmus  to  color  it  distinctly.  Next  add 
dilute  sulphuric  acid  (1  of  acid  to  10  of  water)  drop  by  drop. 

(*")  What  is  its  action  on  a  metal  ?  For  an  answer,  pour 
5  cc.  of  strong  sulphuric  acid  into  40  cc.  of  water  in  a  bottle, 
drop  into  it  some  coarse  iron  filings  or  small  nails,  and 
cover  the  bottle  with  a  square  of  heavy  paper.  In  a  few 
moments  bring  a  lighted  match  to  the  mouth  of  the  bottle, 
lilting  the  cover  at  the  same  moment.  What  chemical 
change  may  have  taken  place  in  this  experiment  ?  Set  the 
bottle  aside  in  order  to  examine  its  contents  in  Exp.  18. 

EXPERIMENT  14. 

Object.  — To  'ascertain  some  characteristics  of  hydrochloric 

acid. 
Manipulation  and  Notes Examine   this   acid   with 

1  Most  chemicals  are  poisonous  or  hurtful.  Tasting  should  never 
be  done  by  the  student  unless  by  direction  found  in  the  book  or  given 
by  the  instructor,  and  then  only  in  the  way  directed. 


30  LABORATORY  STUDIES   IN   CHEMISTRY. 

reference  to  the  same  qualities  exhibited  by  sulphuric  acid 
in  Exp.  13,  and  proceed  by  the  same  directions. 

(a)  What  is  its  taste  ? 

(b)  How  does  it  affect  the  color  of  litmus  ? 

(c)  To  learn  how  it  acts  with  a  metal,  use  zinc,  and  treat 
it  with  acid  diluted  1  to  3.     Preserve  the   contents  of  this 
bottle  for  Exp.  18. 

EXPERIMENT  15. 

Object.  —  To  learn  some  characteristics  of  acetic  acid. 

Manipulation  and  Notes.  —  Learn  its  taste  and  action 
on  litmus  by  directions  in  Exp.  lo  («)  and  (7>)  (note).  For 
its  action  on  metal,  put  10  cc.  of  the  acid  into  a  tube  and 
drop  upon  it  a  short  piece  (about  two  inches)  of  magnesium 
ribbon  (note).  Preserve  this  result  for  Exp.  18. 

Use  iron  instead  of  magnesium,  and  gently  heat  the  acetic 
acid  (note). 

General.  —  Compare  your  results,  and  note  three  impor- 
tant respects  in  which  sulphuric,  hydrochloric,  and  acetic 
acids  are  alike.  Other  acids  are  like  these  three  in  these 
respects. 

EXPERIMENT  16. 

Object.  —  To  ascertain   some  characteristics  of  ammonium 
hydroxide. 

Manipulation  and  Notes.  —  (a)  What  is  its  taste  ? 
Proceed  as  directed  in  Exp.  13. 

(b)  How  does  it  affect  the  color  of  litmus  ?  Make  ready 
two  bottles,  each  half  full  of  water  colored  with  blue  litmus. 
Stir  the  water  in  one  bottle  with  a  glass  rod  wet  with  an 
acid,  and  repeat,  if  necessary,  until  the  color  changes  to  red. 
Then  add,  drop  by  drop,  ammonium  hydroxide,  first  to  the 
blue,  and  afterward  to  the  reddened  litmus. 


ACIDS,    BASES,   AND    SALTS.  31 

EXPERIMENT  17. 

Object.  —  To  compare  some  other  hydroxide  with  ammo- 
nium hydroxide. 

Manipulation  and  Notes.  —  Solutions  of  sodium  hy- 
droxide, potassium  hydroxide,  and  calcium  hydroxide  (lime- 
water)  may  be  used.  Proceed  as  you  did  with  ammonium 
hydroxide,  to  answer  questions  (a)  and  (I). 

General.  —  Compare  the  results,  and  note  the  common 
characteristics  of  these  compounds.  Other  hydroxides  are 
like  these  in  these  respects.  Note  also  the  characteristic 
differences  between  the  hydroxides  and  the  acids.  Hydrox- 
ides are  also  called  bases. 

EXPERIMENT  18. 

Object.  —  To  examine  a  product  of  the  mutual  action  of  a 
metal  and  an  acid. 

Manipulation  and  Notes.  —  Use  iron  with  sulphuric 
acid  or  examine  the  liquid  saved  from  Exp.  13  (c)  as  fol- 
lows :  Pour  off  the  clear  liquid  from  the  sediment  or  resi- 
due of  iron  into  an  evaporating  dish,  and  evaporate  "  to 
crystallization ; "  i.e.,  until  a  solid  appears  when  a  drop  is 
cooled  on  a  glass  rod  or  plate.  Set  the  dish  aside  to  cool 
spontaneously.  Proceed  at  once  to  examine  the  liquids 
saved  from  Exps.  14  and  15  in  the  same  way.  It  may 
be  necessary  to  "  evaporate  to  dryness "  in  some  cases. 
Describe  these  products.  Try  also  to  explain  the  chemical 
changes  which  produced  them. 

General.  —  These  compounds  are  salts.  They  have  been 
produced  by  metals  decomposing  acids,  driving  hydrogen 
out,  and  substituting  themselves  in  its  place.  Sulphuric 
acid  with  iron  yielded  the  salt  named  iron  sulphate,  also 
called  ferrous  sulphate.  Hydrochloric  acid  with  zinc  gave 


82  LABORATORY   STUDIES   IX   CHEMISTRY. 

the  salt  named  zinc  chloride.  Acetic  acid  yiehb  uilts  called 
acetates,  such  as  the  magnesium  acetate  and  the  iron  acetate 
of  Exp.  15. 

EXPERIMENT  19. 

Object  —  To  study  the  mutual  action  of  acids  and  bases. 

Manipulation  and  Notes.  —  Use  hydrochloric  acid  and 
sodium  hydroxide.  Put  5  cc.  of  hydrochloric  acid  into  a 
bottle  or  beaker,  and  drop  into  it  a  small  bit  of  litmus 
paper,  which  instantly  becomes  red.  Next  add  a  solution 
of  sodium  hydroxide,  little  by  little,  shaking  or  stirring 
the  liquid  well  after  each  addition.  Watch  the  color  of  the 
litmus  paper;  it  will  after  a  while  show  signs  of  turning 
blue.  Then  add  the  hydroxide  carefully,  a  drop  at  a 
time,  until  after  the  last  drop  the  paper  remains  blue. 
Then  add  a  drop  of  dilute  hydrochloric  acid :  the  paper 
should  neither  be  distinctly  blue  nor  red,  but  purple.  By 
this  sign  you  know  that  the  acid  and  base  are  neutralized 
by  each  other. 

Next  search  for  the  product  of  the  action.  Put  the 
liquid  into  a  porcelain  dish,  and  evaporate  it  carefully  until 
dry.  Let  the  residue  cool.  Note  its  color  and  its  taste. 
What  does  it  seem  to  be  ?  Is  it  a  salt,  according  to  the 
definition  of  that  term  ? 

EXPERIMENT  2O. 

Object.  —  To  compare,  the  products  obtained  by  the  action  of 
the  metal  sodium,  and  of  the  sodium  hydroxide,  on  hydro- 
chloric, add. 

Manipulation  and  Notes (a)    Measure  2  cc.  of  strong 

hydrochloric  acid  into  a  test  tube  which  stands  in  the  rack. 
Drop  in  upon  it  a  piece  of  sodium  as  large  as  a  very  small 
pea,  and  instantly  cover  the  mouth  of  the  tube  loosely  with 
a  piece  of  paper.  After  half  a  minute,  test  the  gas  with  a 


ACIDS,   BASES,   A^B\$ALT&^*§^         33 

match  flame.  When  the  sodium  has  disappeared,  drop  in  an- 
other piece  of  about  the  same  size,  and  afterward  a  third. 

(b)  To  examine  the  product :  Let  it  settle  to  the  bottom 
of  the  tube,  and  then  pour  off  the  liquid  so  carefully  that 
you  leave  the  solid  behind  almost  dry.  In  this  way  you 
get  rid  of  most  of  the  acid  which  was  not  decomposed. 
Then  add  water  enough  to  dissolve  the  solid.  Pour  the 
solution  into  a  small  porcelain  dish,  and  heat  it  over  a 
small  flame  until  the  water  is  all  driven  off  and  the 
solid  remains  dry  and  white.  The  dish  must  now  stand 
until  cold,  after  which  add  a  few  drops  of  water.  Taste 
the  solution.  Compare  the  product  with  that  obtained  in 
Exp.  19.  Should  you  call  this  product  a  salt  ?  Why  ? 

General.  —  The  action  of  the  acid  and  base  in  Exp.  19 
is  typical.  By  their  mutual  action,  when  mixed  in  solu- 
tion, an  acid  and  a  base  neutralize  each  other,  or,  in  other 
words,  mutually  decompose  each  other  to  form  two  new 
compounds,  neither  of  which  is  an  acid  or  a  base.  One  of 
them  is  a  salt :  the  other  is  water.  The  foregoing  experi- 
ments show  that  salts  may  be  produced  in  two  ways 
(explain). 


34 


LABORATORY   STUDIES  IN   CHEMISTRY. 


IV.     DEFINITE   PROPORTIONS. 


EXPERIMENT   21. 

Object.  —  To  ascertain  whether.,  ivhen  hydrochloric  acid  and 
sodium  hydroxide  neutralize  each   other,   there   is   any 
particular  relation  between  the  quantities  required. 
Manipulation  and  Notes.  —  Mix  2  cc.  of  hydrochloric 
acid  with  100  cc.  of  water.     Mix  15  cc.  of 
sodium-hydroxide  solution  with   100  cc.  of 
water.      Prepare  two  burettes.     Rinse  one 
with  water,  and  then  with  2  or  3  cc.  of  the 
dilute  hydrochloric  acid,  and  support  it  in 
a  clamp  (h,  Fig.  17).     Rinse  the  other  with 
water,  and  afterward  with  2  or  3  cc.  of  the 
dilute  sodium  hydroxide,  and  support  it  in 
a  clamp,  s.     See  that  the  tips  of  both  are 
closed  by  their  pinchcocks. 

Fill  the  burette  h  with  the  dilute  acid, 
and  the  burette  s  with  the  dilute  hydroxide. 
Draw  off  from  each  by  pressing  the  pinch- 
cock  until  the  bottom  of  the  meniscus  (the 
curved  upper  surface  of  the  liquid)  is  ex- 
actly level  with  the  zero  mark  on  the  burette. 
(Be  careful  to  place  your  eye  on  a  level  with  the  mark,  so 
that  your  sight  shall  not  slant  upward  or  downward.) 

Run  out  exactly  10  cc.  of  the  acid  into  a  small  beaker, 
and  add  a  drop  of  litmus  solution.  Then  add  from  the 
burette  s  the  hydroxide  little  by  little,  keeping  it  mixed 
by  shaking  the  beaker,  and  toward  the  last  carefully,  drop 


Fig.    17. 


DEFINITE  PROPORTIONS. 


35 


by  drop,  until  the  change  of  color  to  purplish  blue  shows 
that  the  acid  is  neutralized.  Note  the  number  of  cubic 
centimeters  used. 

Repeat,  using  15  cc.  of  the  acid ;  and  again,  using  20  cc. 
of  the  acid.  Then  hnd  in  each  case  the  ratio  of  the  quan- 
tities of  acid  and  base,  extending  the  division  to  one 
decimal  place. 

Record  your  results  in  tabular  form,  as  follows :  — 


Acid  used. 

Hydroxide 
required. 

cc.  of  Hydroxide 
for  1  cc.  Acid. 

10  cc 

-•  cc 

15  cc. 

cc. 

20  cc. 

cc. 

Are  the  quantities  of  base  for  1  cc.  of  acid  very  different  ? 

Is  the  difference  so  small  that  it  may  be  due  to  the  neces- 
sary lack  of  exactness  (give  reason)  in  your  experiment  ? 

Would  you  conclude  that  a  given  quantity  of  one  of 
these  liquids  would  in  every  case  require  a  definite  quantity 
of  the  other,  or  not  ? 

Does  each  cubic  centimeter  of  this  dilute  acid  contain  the 
same  mass  of  acid  as  every  other  ?  Does  the  chemical 
action  take  place  between  definite  masses,  or  without  regard 
to  the  proportions  ? 

EXPERIMENT  22. 

Object.  —  To  ascertain  whether,  when  hydrochloric  acid  and 

sodium  carbonate  react,   there   is  any  definite  relation 

between   the  mass  of  the  carbonate  used  and  the  mass 

of  sodium  chloride  produced. 

Manipulation  and  Notes.  —  (a)  Weigh  a  clean  and  dry 

porcelain  dish.     Add  5  g.  of  crystallized  sodium  carbonate, 


36  LABORATORY  STUDIES  IN   CHEMISTRY. 

selecting  small  crystals  which  have  no  white  spots  (give 
reason).  Pour  in  dilute  hydrochloric  acid  little  by  little, 
until  the  carbonate  is  dissolved,  taking  care  that  no  loss 
occurs  by  effervescence. 

Place  the  dish  over  a  small  flame,  and  evaporate  slowly 
to  dryness,  without  loss,  which  toward  the  end  of  the  opera- 
tion requires  watchful  care.  Do  not  press  the  heat  after 
the  salt  is  dry,  else  loss  will  occur  by  decrepitation  (give 
reason).  When  cold,  see  that  the  outside  of  the  dish  is 
clean  and  dry,  and  then  weigh  it  with  its  contents. 

Weight  of  dish  and  sodium  chloride  =  ---         --  g. 
Weight  of  dish  alone  --  g. 

Weight  of  the  sodium  chloride  --  g. 

Hence  5  g.  of  sodium  carbonate  yield g.  of  sodium 

chloride. 

(&)  Repeat  the  foregoing  operations  with  10  g.  of  sodium 
carbonate. 

Compare  the  results  of  (a)  and  (7/),1  and  decide  whether 
equal  masses  of  sodium  carbonate  will  yield  the  same  mass 
of  sodium  chloride. 

1  It  is  well  to  give  different  quantities  of  sodium  carbonate  to  dif- 
ferent members  of  a  class,  and  thus  secure  more  data  for  discussion. 


WATER.  37 


V.     WATER. 


EXPERIMENT  23. 
Object.  —  To  ascertain  whether  water  is  usually  pure. 

Manipulation  and  Notes.  —  (a)  Does  it  hold  any  solid 
impurity  ?  Evaporate  to  dryness  100  cc.  of  ordinary  spring 
or  hydrant  water  in  a  porcelain  dish  (note). 

(b)  Does  it  hold  any  gaseous  impurity  ?      Fill  a  flask, 
1,000  cc.  capacity  (a  smaller  one  will  serve),  with  freshly 
drawn    spring  or  hydrant  water.     Invert   it,  and   leave  it 
standing,  mouth  down,  in  a  water  pan  for  several  hours,  in 
a  warm  place  (note). 

(c)  Evaporate  some  recently  caught  rain  water,  and  com- 
pare its  purity  with  that  of  water  used  in  operation  (a). 

What  are  the  constituents  of  pure  water  ?    (See  Exp.  12.) 

EXPERIMENT  24. 

Object.  —  To  discover  the  effect  of  contact  of  water  with  some 
solid  substances. 

Manipulation  and  Notes.  —  (a)  Fill  a  bottle  three 
fourths  full  of  clear  water.  Cover  it  with  a  piece  of  muslin 
loosely,  and  bind  the  cover  in  place  by  a  string  around  the 
neck  (Fig.  18).  Mix  half  a  teaspoonful  of  powdered  cochi- 
neal with  a  larger  quantity  of  sand  or  soil.  Place  the  mix- 
ture on  the  cover,  and  then  pour  some  clear  water  slowly 
upon  it.  What  is  the  result  ? 

The  liquid  which  you  obtain  is  called  a  solution  of 
cochineal.  What  would  you  obtain  by  evaporating  it  ? 
Try  it. 


LABORATO11Y    STUDIES    IN    CHEMISTRY. 

Bepeat  the  experiment,  but  in  place  of  the  cochineal 
use  some  powdered  copper  sulphate  (note). 

Name    the    liquid    you   obtain.      Prove,  by 
evaporation,  that  it  contains  copper  sulphate. 
Can  you  now  explain  the  presence  of  solid 
impurities  in  spring  water  ? 

Is  the  dissolving  of  copper  sulphate  a  chem- 
F>g7i8.  ical  change  ? 

EXPERIMENT    25. 

Object.  —  To  ascertain  whether  the  quantity  of  a  solid  soluble 
in  a  given  volume  of  water  is  limited. 

Manipulation  and  Notes.  —  Measure  10  cc.  of  water 
into  a  test  tube.  "Keduce  the  given  solid  to  fine  powder. 
Introduce  a  small  portion.  Close  the  tube  with  the  thumb, 
and  shake  vigorously.  If  this  portion  is  completely  dis- 
solved, add  a  second,  and  proceed  as  be  fore ;  then  perhaps 
a  third.  In  any  case,  continue  to  add  small  portions  until 
your  object  is  accomplished.  Use  (H)  copper  sulphate, 
(b)  sodium  chloride,  (V)  barium  sulphate. 

Place  these  tubes  with  their  contents  aside,  to  be  used  in 
the  next  experiment. 

If  the  first  small  portion  does  not  disappear,  so  that  you 
cannot  decide  whether  any  at  all  has  been  dissolved,  you 
should  decant  the  clear  water  from  the  solid,  or  filter  it, 
and  then  evaporate  it  to  dryness. 

Write  your  conclusion.  I'oint  out  the  difference  observed 
in  the  three  substances. 

EXPERIMENT    26. 

Object.  —  To  ascertain  the  effect  of  heat  on  the  solvent  power 

of  water. 

Manipulation  and  Notes. —Warm  the  tube  containing 
the  excess  of  solid  which  could  not  dissolve  in  cold  water, 


WATER.  39 

and  observe  whether  the  solid  disappears.  Continue  the 
heat,  if  need  be,  until  the  water  boils.  If  in  any  case  the 
solid  disappears,  add  another  small  portion  and  continue 
the  heat.  Repeat  until  the  liquid  is  saturated;  i.e.,  con- 
tains all  it  can  hold  of  the  solid  in  solution. 

Use  tubes  (a),  (b),  and  (c)  of  the  preceding  experiment. 
Write  your  conclusion  with  respect  to  each  substance.  Let 
the  tubes  stand  until  cold  (note  ;  explain). 

EXPERIMENT   27. 
Object. —  To  ascertain  the  solubility  of  a  solid. 

Explanation.  —  The  solubility  of  a  solid  is  described  in 
two  ways,  —  either  by  stating  the  mass  (usually  called  the 
weight)  which  can  be  dissolved  in  100  cc.  of  the  solvent,  or 
by  stating  the  volume  of  the  saturated  liquid  which  holds 
a  unit  of  mass  (1  g.  of  the  solid)  in  solution. 

Manipulation  and  Notes.  —  (a)  For  the  solubility  of 
barium  chloride,  place  20  cc.  of  water  in  a  large  test  tube 
or  small  beaker.  Add  a  portion  of  finely  powdered  chloride, 
and  gradually  heat  to  boiling.  If  this  portion  completely 
dissolves,  add  another.  Repeat  until  the  hot  liquid  is  satu- 
rated. Cool  the  solution  (note).  When  quite  cold,  filter  it. 
Measure  15  cc.  of  the  clear  solution  into  a  weiyhed,  clean 
porcelain  dish,  and  evaporate  to  dryness.  Let  no  loss  occur. 

Cover  the  dish,  and  let  it  cool.  When  quite  cold,  see 
that  the  outside  of  the  dish  is  clean,  and  weigh  *  it. 

Mass  of  dish  and  residue,  =   g. 

Mass  of  dish  •  g. 

Mass  of  the  residue  alone  =  g. --  A 

15  -r  A  —  ....  B  =  No.  cc.  of  solution  holding  1  g.  of  barium  chloride. 

The  solubility  of  barium  chloride  in  cold  water  is  1  g. 
to  B  cc. 

1  The  balance  gives  the  inaxses  of  bodies,  but  the  masses  are  pro- 
portional to  the  weight*  in  any  one  locality. 


40 


LABORATORY    STUDIES    IN    CHEMISTRY. 


(b)1  Find  the  solubility  of  sodium  chloride  in  cold  water, 
(c)    Find  the  solubility  of  copper  sulphate  in  cold  water. 

EXPERIMENT    28. 

Object.  —  To  leafn  whether  water    boils  at  any  particular 

temperature. 

Manipulation  and  Notes.  —  Put  water  into  an  open 
flask,  and  support  it  by  a  clamp.  Heat  it  gradually.  Put 
the  bulb  of  a  thermometer  into  the  water,  and  watch  its  in- 
dications. Continue  this  until  the  water  boils  freely,  and 
for  some  time  afterward  (note].  Raise  the  bulb  into  the 
vapor  above  the  water  (note,  and  draw  conclusions). 

EXPERIMENT   29. 

Object. —  To  determine  the  boiling  point  of  water. 
Manipulation  and  Notes.  —  Place  sufficient  water  in  a 
side-neck  flask  to  fill  it  about  one 
fourth  full,  and  close  it  with  a  cork 
through  which  extends  the  stem  of 
a  thermometer,   as  shown  in  Fig. 
19,  the  bulb  a  little  below  the  open- 
ing into  the  side  neck.     To  the  side 
neck  join  a  long 
glass   tube    by   a 
rubber    connec- 
tion.   Put  the  end 
of  the  glass  tube 
down  into  a  test 
F'9-  w-  tube  which   rests 

in  the  water  pan  nearly  filled  with  cold  water,  and  finally 
heat  the  flask  with  a  Bunsen  lamp. 

1  A  class  may  very  well  be  divided  into  sections,  to  each  of  which 
a  single  substance  is  assigned.  The  results  of  all  may  be  discussed 
together. 


WATER.  41 

Note  every  effect  you  can  see  while  the  water  is  being 
heated,  but  especially  the  effect  on  its  temperature  before 
and  during  the  ebullition.  If  the  temperature  becomes 
constant  while  the  water  boils,  read  and  note  it  as  the 
boiling  point. 

Examine  the  substance  in  the  test  tube.  What  is  it,  and 
how  came  it  there  ?  Decide,  by  evaporating  it,  whether  it 
is  purer  than  the  water  in  the  flask. 

General.  —  In  like  manner  the  boiling  points  of  other 
liquids  may  be  found.  The  object  of  the  delivery  tube,  test 
tube,  and  water  pan  is  to  collect  the  substance  instead  of 
letting  it  pass  into  the  air.  They  may  be  dispensed  with  if 
there  is  no  objection  to  letting  the  vapor  escape.  When 
the  vapor  is  collected  and  condensed,  the  process  is  called 
distillation.  This  is  the  most  important  method  of  purify- 
ing water  and  other  liquids. 

EXPERIMENT   SO. 

Object. — To  compare  the  boiling  points  of  water  and  alcohol. 
Repeat  Exp.  29  with  alcohol  instead  of  water. 

EXPERIMENT    31. 

Object. —  To  find  the  density  of  water  and  of  alcohol. 

Explanation.  —  The  density  of  a  substance  is  described 
by  stating  the  mass  of  the  substance  contained  in  1  cc.  or 

in  a  unit  volume. 

Mass  in  grams 

Density  =  - 

Volume  in  cubic  centimeters 

Manipulation  and  Notes.  —  (a)  Weigh  a  clean,  dry 
beaker ;  add  20  cc.  of  cold  water ;  take  its  temperature  ; 
weigh  the  beaker  and  water,  and  make  the  necessary  calcu- 
lation. Finally  state  your  result  as  follows  :  — 

RESULT:  The  density  of  water  at °  C.  is g.  per  cc. 


42  LABORATORY  STUDIES   IN  CHEMISTRY. 

(b)  Repeat  the  operations,  using  alcohol  at  the  tempera- 
ture of  the  room.  State  the  result  as  follows  :  — 

RESULT:  The  density  of  alcohol  at °  C.  is g.  per  cc. 

Divide  the  density  of  alcohol  by  that  of  water.  The 
quotient  is  the  relative  density  of  alcohol.  State  your 
result  as  follows  :  — 

RESULT:  The  relative  density  of  alcohol  at °  C.  is 

General.  —  In  like  manner,  the  densities  and  the  relative 
densities  of  other  liquids  may  be  found. 

EXPERIMENT   32. 

Object.  —  To   compare   the    action   of  water  with  that  of 
hydrochloric  acid  on  sodium  carbonate. 

Manipulation  and  Notes.  —  Place  1  g.  of  sodium  car- 
bonate in  a  small  porcelain  dish,  add  about  5  cc.  of  water, 
and  stir  the  mixture  until  the  solid  disappears  (note).  To 
learn  whether  a  chemical  change  has  occurred,  evaporate 
the  solution  to  dryness,  and  see  whether  the  carbonate  is 
restored  unchanged  (note). 

Add  dilute  hydrochloric  acid  to  1  g.  of  sodium  carbonate 
until  the  solid  is  dissolved  (note).  Evaporate  the  solution 
slowly,  compare  the  dry  product  with  the  original  carbon- 
ate (note))  and  judge  whether  a  chemical  change  occurred. 

General.  —  These  results  should  show  that  solutions 
sometimes  involve  only  physical  changes,  and  sometimes 
chemical  changes.  Water  solutions  are  usually  physical 
solutions ;  acid  solutions  are  usually  chemical.  With  di- 
lute acid  the  action  is  both  physical  and  chemical.  In  this 
experiment,  for  example,  the  carbonate  was  chemically 
changed  into  the  chloride,  and  then  the  water  which  was 
present  dissolved  the  chloride  without  change. 


HYDROCHLORIC-ACID   AND   OTHER    CHLORIDES.    43 


VI.     HYDROCHLORIC-ACID   AND   OTHER 
CHLORIDES. 


EXPERIMENT   33. 

Object.  —  To  obtain  hydrochloric  acid,  and  study  its  prop- 
erties. 

Manipulation  and  Notes. — (a)  Hydrochloric  acid  may 
be  prepared  by  the  mutual  action  of  sodium  chloride  and 
sulphuric  acid.  To  12  cc.  of  water  in  a  beaker  add  slowly, 
and  with  constant  stirring,  33  cc.  of  strong  sulphuric  acid. 
While  this  acid  is  cooling,  set  up  the  apparatus,  consist- 
ing of  a  side-neck  flask,  three  conical  flasks,  and  a  bottle. 
The  connections  would  better  be  all  glass  (Fig.  8,  p.  20). 
The  flasks  should  be  dry.  Connect  flasks  a  and  b  with 
long  tubes  toward  the  generator.  Join  c  with  short  tube 
toward  generator,  and  to  its  long  tube  join  a  delivery  tube 
reaching  into  the  bottle.  Put  50  cc.  of  water  into  the 
bottle,  and  let  the  tube  dip  into  it.  All  joints  should  be 
proved  to  be  tight.  When  the  connections  are  all  made, 
put  into  the  generator  about  35  g.  of  sodium  chloride.  Pour 
upon  it  rapidly  the  45  cc.  of  the  cold  diluted  acid,  and 
quickly  insert  the  stopper  of  the  flask.  Close  the  holes  of 
a  Bunsen  burner ;  turn  the  flame  down  to  a  height  less 
than  an  inch ;  place  it  below  the  generator,  with  the  flame 
not  touching  the  glass.  If  the  gas  is  given  off  too  rap- 
idly, remove  the  heat  until  it  slackens.  Describe  all  the 
changes.  Note  especially  what  takes  place  in  the  water, 
and  explain  it. 

(b)  Remove  the  stopper  from  flask  b,  and  invert  the 
flask  with  its  mouth  in  a  vessel  of  water  (note). 


44  LABORATORY  STUDIES  IN  CHEMISTRY. 

What  property  of  the  gas  does  this  result  reveal  ? 

(c)  What  is   its   behavior  toward  flame  ?     Kemove  the 
stopper  from  c,  and   insert  a  splinter  flame  (note).     Then 
invert  the  flask  in  water  (give  reason). 

(d)  How  does  its  solution  behave  toward  litmus  ?     Place 
blue-litmus  solution  in  a  test  tube,  and  add  a  little  of  the 
gas  solution  from  the  bottle  (note). 

(e)  How  does  it  behave  toward  solution  of  silver  nitrate  ? 
To  a  very  dilute  solution  of  silver  nitrate  in  a  test  tube  add 
a  few  drops  of  the  gas  solution  (note).1 

End  the  Experiment.  —  If  the  generator  is  cold,  close 
its  side  neck.  Invert  it  with  its  mouth  under  water  in  a 
pan.  When  the  gas  has  been  all  absorbed,  the  tiasks  and 
generator  may  be  emptied  and  cleansed. 

EXPERIMENT    34. 

Object.  —  To  liberate  chlorine  from  hydrochloric  acid. 

Manipulation  and  Notes.  —  Put  1  or  2  g.  of  manga- 
nese dioxide  in  a  test  tube  by  sliding  it  to  the  bottom  along 
a  little  paper  trough  (in  this  way  you  keep  the  oxide  from 
soiling  the  tube).  Pour  upon  the  oxide  1  cc.  of  strong 
hydrochloric  acid.  Close  the  tube  loosely  with  the  finger. 
Wait  until  the  acid  lias  moistened  the  oxide  completely, 
and  then  warm  it  by  holding  it  above  the  tip  of  a  very  low 
flame.  Just  as  soon  as  the  tube  seems  almost  full  of  the 
product,  remove  the  heat.  (Caution :  do  not  breathe  this 
gas  !  Do  not  drive  it  off  into  the  air.)  Describe  the  gas. 

Cautiously  open  the  tube  and  insert  a  narrow  strip  of 
blue  litmus  paper  (note). 

End  the  Experiment.  —  Invert  the  tube  and  uncover  its 
mouth  under  water.  Leave  it  thus  so  long  as  gas  can  be  seen 
in  it.  What  property  of  the  gas  does  this  result  reveal  ? 

1  The  liquid  hydrochloric  acid  of  the  laboratory  is  a  strong  solution 
of  hydrochloric-acid  gas  in  water. 


HYDROCHLORIC-ACID  AND   OTHER    CHLORIDES.    45 

EXPERIMENT   35. 

Object.  —  To  study  the  mutual  action  of  hydrochloric  acid 
and  iron. 

Manipulation  and  Notes.  — Into  o  cc.  of  strong  hydro- 
chloric acid  put  several  small  bits  of  iron,  such  as  small 
tacks.  Test  the  gas  (note).  Let  the  tube  stand  until  the 
action  is  over.  Describe  the  solution.  Obtain  the  solid 
from  solution  by  filtering  and  evaporation.  Describe  this 
ferrous  chloride. 

General.  —  This  experiment  is  typical.  Several  other 
metals  may  be  converted  into  their  chlorides  in  the  same 
way. 

EXPERIMENT   36. 

Object.  —  To  study  the  effect  of  nitric  acid  upon  the  action 
of  hydrochloric  acid  and  iron. 

Manipulation  and  Notes.  —  (a)  Dissolve  the  ferrous 
chloride  obtained  in  Exp.  35  in  a  little  water.  Add  a  few 
drops  of  strong  nitric  acid,  and  heat  to  boiling  (note).  Evap- 
orate, and  compare  residue  with  the  ferrous  chloride  used. 

(b)  Put  2  cc.  of  strong  hydrochloric  acid  into  a  test  tube, 
and  add  about  one  fourth  as  much  strong  nitric  acid  (note). 
Into  this  drop  two  or  three  small  tacks  (note). 

When  the  action  is  over,  evaporate,  and  decide  whether 
the  residue  is  ferrous  chloride  or  the  substance  found  ki 
(«),  or  something  else. 

General.  —  This  experiment  is  typical.  Nitric  acid 
changes  the  lower  compounds  of  many  substances  into  the 
higher  as  it  changed  the  ferrous  chloride  into  ferric  chlo- 
ride in  (a).  On  this  account  it  is  called  an  oxidizing  agent. 
A  mixture  of  strong  hydrochloric  acid  and  strong  nitric 
acid  is  known  as  aqua  regia.  It  contains  free  chlorine,  and 
chlorine  in  unstable  combination,  by  which  the  highest 
chloride  of  a  metal  is  formed  at  once,  as  in  (b). 


46          LABORATORY  STUDIES  IN   CHEMISTRY. 


VII.     THE   CHLORINE   GEOUP. 


EXPERIMENT   37. 

Object.  —  To  liberate  chlorine,  iodine,  and  bromine  from 
their  compounds  of  sodium  or  potassium. 

Manipulation  and  Notes.  —  (a)  Chlorine.  Pour  1  cc. 
of  strong  sulphuric  acid  into  1  cc.  of  water  in  a  test  tube. 
Mix,  and  set  aside  to  cool.  Mix  i  g.  of  dry  sodium  chlo- 
ride with  ^  g.  of  manganese  dioxide.  When  the  acid  is 
cold,  introduce  the  mixture  of  salt  and  oxide  without  soil- 
ing the  walls  of  the  tube.  Cover  the  tube  with  the  linger, 
hold  it  nearly  horizontal,  and  warm  the  mixture  very  gently. 
Withdraw  the  heat  as  soon  as  the  action  is  well  started,  that 
the  gas  shall  not  be  driven  into  the  air.  Do  not  breathe  the 
gas  nor  air  containing  much  of  it  (note).  Lower  a  splinter 
flame  just  into  the  upper  layer  of  the  gas  (note).  Lower 
a  narrow  strip  of  litmus  paper  into  the  gas  (note).  Finally 
invert  the  tube  in  a  pan  of  water  to  keep  the  gas  out  of 
the  atmosphere.  Write  and  explain  the  reaction  which 
occurred. 

(b)  Bromine.  Proceed  exactly  as  in  (a),  using  £  g.  of 
sodium  or  potassium  bromide  mixed  with  1  g.  of  manganese 
dioxide,  and  1  cc.  of  acid  prepared  by  adding  1  cc.  of 
strong  sulphuric  acid  to  5  cc.  of  water.  Do  not  breathe  the 
vapors !  Note  color  and  odor.  Observe  the  cold  walls 
of  the  tube  (note).  Introduce  a  splinter  flame  just  inside 
the  mouth  of  the  tube  (note}.  Introduce  a  strip  of  moist 
litmus  paper  (note).  Invert  in  water.  Write  and  explain 
the  reaction  by  which  bromine  was  set  free. 


THE   CHLORINE   GROUP.  47 

(c)  Iodine.    Proceed  exactly  as  in  (a),  using  acid  of  the 
same  strength  with  a  mixture  of  1  g.  of  sodium  or  potassium 
iodide  with  2  g.   of   manganese  dioxide.     Do  not  breathe 
the  vapors  (note).     Test  with  flame  (note)  and  with  litmus 
paper  (note}.     Observe  the  upper  cold  walls  of   the    tube 
(note).     Invert  in  water.     Note  whether  the  chlorine,  the 
bromine,   and  the   iodine  are   absorbed  by  the  water,  and 
judge  their  solubilities.     Write  and  explain  the  reaction  by 
which  iodine  was  set  free. 

(d)  Put  a  few  crystals  of  iodine  into  a  dry  tube,  and  add 
a  very  little  alcohol.     Judge  the  solubility  of  iodine  in  alco- 
hol (note).    The  strong  solution  is  called  tincture  of  iodine. 

General.  - —  In  the  foregoing  study  you  can  detect  the 
very  great  chemical  resemblance  of  the  three  elements 
(explain).  You  also  find  some  marked  differences  (explain). 
Their  chemical  resemblance  is  shown  in  all  their  reactions, 
and  in  the  composition  of  all  their  compounds. 

EXPERIMENT  38. 

Object.  —  To  compare  the  chemical  actions  of  chlorides,  bro- 
mides, and  iodides. 

Manipulation  and  Notes.  —  1.  With  Silver  Nitrate. 
Arrange  three  test  tubes  with  2  cc.  of  pure  water  in  each. 
Add  to  one,  5  drops  of  strong  solution  of  any  chloride 
(sodium  chloride)  ;  to  a  second,  5  drops  of  a  strong  solu- 
tion of  any  bromide  (potassium)  ;  and  to  a  third,  5  cc. 
of  any  iodide  (potassium).  Treat  the  mixtures  in  suc- 
cession as  follows :  — 

(a)  Add  silver  nitrate  drop  by  drop,  shaking  the  tube 
vigorously  after  each  addition,  until  a  drop  fails  to  make  a 
precipitate.  Describe  the  precipitates.  Note  the  effect  of 
shaking  them.  Look  carefully  for  some  difference  in  their 
colors. 


48          LABORATORY  STUDIES  IN  CHEMISTRY. 

(b)  Then  expose  the  tubes  to  sunlight,  or  for  some  time 
to  diffuse  light,  and  note  the  changes  which  occur  in  the 
colors. 

Which  are  most  marked,  —  the  resemblances,  or  the  dif- 
ferences, seen  in  these  reactions  ?  Note  the  differences  with 
care. 

(c)  Next  test  the  solubility  of  these  precipitates  in  am- 
monium hydrate.     To  do  this,  make  a  little  fresh  precipi- 
tate, and  keep  it  from  light  as  much  as  possible.     When  the 
precipitate  has  settled,  decant  the  liquid  carefully,  so  as  to 
leave    the    precipitate    in    the    tube.     Then   pour   upon    it 
ammonium  hydrate  gradually,  with  shaking,  until  you  can 
decide  whether  the  precipitate  dissolves. 

Compare  the  solubilities  with  care  (note). 

2.  With  Starch.  Make  a  very  thin  starch  water  by  boil- 
ing a  minute  piece  of  starch  in  considerable  water,  and 
cooling  the  liquid.  Dissolve  a  chloride,  a  bromide,  and  an 
iodide,  each  in  water,  but  with  this  difference :  make  the 
bromide  very  concentrated,  and  the  iodide  very  dilute. 

To  a  part  of  each  solution  add  a  few  drops  of  nitric 
acid,  with  this  difference  :  for  the  iodide  use  the  acid 
diluted  one  to  one.  Add  a  little  of  the  starch  water. 
There  should  be  a  difference  in  color  produced  :  note  it 
carefully. 

To  another  part  of  each  solution  add  a  little  of  the  cold 
starch  water,  without  the  nitric  acid.  By  this  means  you 
can  decide  whether  nitric  acid  is  necessary  to  bring  out  the 
colors  observed  before. 

Add  the  starch  water  to  hot  solutions  instead  of  cold  ones, 
and  let  them  become  cold.  By  this  means  you  will  learn 
the  effect  of  heat. 

Compare  the  chloride,  bromide,  and  iodide  in  these  reac- 
tions with  great  care.  Note  differences. 


THE   CHLORINE   GROUP.  49 

General.  —  In  this  study  you  have  found  more  proof  of 
the  chemical  resemblance  of  chlorine,  bromine,  and  iodine. 
You  have  also  seen  the  differences  by  which  you  would  be 
able  to  distinguish  chlorides,  bromides,  and  iodides  from 
one  another. 

For  practice,  take  a  few  substances  from  the  teacher,  or 
a  friend  who  knows  what  they  are,  and  see  if  you  can 
decide  whether  each  is  a  chloride,  a  bromide,  or  an  iodide. 


50  LABORATORY   STUDIES  IN   CHEMISTRY. 


VIII.    SULPHUR  AND  SOME  OF  ITS  COMPOUNDS. 


I.     Sulphur  and  the  Sulphides. 

EXPERIMENT    39. 

Object.  —  To  ascertain  the  effect  of  heat  on  sulphur. 

Manipulation  and  Notes.  —  Reduce  a  piece  of  brim- 
stone to  small  fragments,  and  half  fill  a  test  tube  with  it. 
Hold  the  tube  in  the  hot  air  above  the  lamp  flame,  and  thus 
keep  it  from  contact  with  too  strong  a  heat,  but  lower  it 
until  you  find  the  heat  just  intense  enough  to  melt  the 
sulphur.  Can  you  melt  it  without  changing  the  color  of 
the  liquid  (note)  ? 

Place  the  tube  with  the  limpid  liquid  sulphur  where  it 
will  not  be  shaken,  and  watch  the  liquid  while  it  slowly 
cools  (note). 

Now  carefully  re-melt  the  sulphur,  and  then  make  the 
liquid  a  little  hotter,  —  only  a  little  (note). 

Continue  to  heat  the  liquid  gradually,  and  incline  the 
tube  from  time  to  time,  until  it  is  nearly  horizontal 
(note). 

Then  heat  it  still  more,  and  test  from  time  to  time  its 
power  to  flow. 

Continue  to  apply  heat  to  find  out  whether  the  sulphur 
can  be  boiled,  and  what  is  the  color  of  the  vapor  (note). 

Pour  the  somewhat  viscid,  dark  liquid  in  a  small  stream 
into  a  vessel  of  cold  water,  and  examine  the  sulphur  after 
this  sudden  cooling  (note). 


SULPHUR   AND   SOME   OF  ITS   COMPOUNDS.       51 


EXPERIMENT    4O. 

Object.  —  To  convert  copper  into  copper  sulphide. 

Manipulation  and  Notes.  —  Prepare  a  small  coil  of  fine 
copper  wire  by  winding  the  wire  around  a  glass  tube.  Heat 
a  small  piece  of  sulphur  to  boiling  in  a  tube.  Insert  the 
coil,  and  continue  the  heat  for  a  minute.  Describe  the 
change  which  the  copper  has  undergone. 

The  experiment  may  be  made  by  mixing  4  g.  of  flowers  of 
sulphur  with  8  g.  of  fine  copper  filings,  and  heating  this 
mixture  in  a  test  tube  (note). 

General.  —  This  experiment  is  typical.  Similarly  many 
other  metals  may  be  converted  into  their  sulphides  by  the 
direct  action  of  sulphur. 

EXPERIMENT   41. 

Object.  —  To  obtain  hydrogen  sulphide  from  hydrochloric 
acid  and  ferrous  sulphide. 

Manipulation  and  Notes.  —  Put  a  piece  of  ferrous  sul- 
phide not  larger  than  a  grain  of  wheat  into  a  test  tube,  and 
pour  upon  it  1  cc.  of  dilute  hydrochloric  acid  (half  water) 
(note). 

Notice  with  care  the  odor  in  the  tube  (note). 

Test  the  gas  with  flame  (note). 

Notice  the  color  of  the  liquid  when  the  action  is  over. 

Write  and  explain  the  reaction. ' 

General.  —  This  experiment  typifies  the  action  of  strong 
acids  on  sulphides  generally.  It  also  teaches,  that,  in  the 
preparation  and  use  of  hydrogen  sulphide,  there  should  be 
the  utmost  care  to  prevent  its  escape  into  the  room  (give 
reason}. 

Given  a  metallic  compound,  how  would  you  proceed  to 
determine  whether  it  is  a  sulphide  ? 


52  LABORATORY  STUDIES  IN  CHEMISTRY. 

EXPERIMENT   42. 

Object.  —  To  prepare  hydrogen  sulphide,  and  to  learn  some- 
thing of  its  character. 

Manipulation  and  Notes.  —  Set  up  the  usual  gas  appa- 
ratus, consisting  of  a  side-neck  flask,  with  three  collecting 
flasks,  a,  b,  c,  and  bottle  (Fig.  8,  p.  20).  Put  water  enough 
in  a  to  cover  the  end  of  the  long  tube  when  inserted.  Put 
about  the  same  quantity  in  b,  and  add  1  cc.  of  solution  of 
copper  chloride.  Put  water  and  a  little  zinc-acetate  solu- 
tion in  c,  and  into  the  bottle  put  dilute  ammonium  hydrox- 
ide (half  water).  Connect  with  long  tubes  toward  generator. 
Prove  the  joints  to  be  air-tight  (give  reason). 

Finally  slide  about  10  g.  of  ferrous  sulphide  into  the  flask. 
Add  30  cc.  of  hydrochloric  acid  (half  water).  Quickly  close 
the  flask  air-tight.  Pay  careful  attention  to  what  occurs  in 
each  flask  in  succession  (note). 

Let  the  action  go  on  until  effervescence  ceases.  Then 
disconnect  c  and  the  bottle,  also  a  and  the  generator.  Open 
the  side-neck  flask.  Quickly  cover  its  mouth  with  the  hand, 
and  invert  it  in  water  in  the  water  pan  (give  reason). 

Proceed  with  the  study  as  follows :  Take  flask  a  out  of 
the  series  without  removing  the  stopper ;  transfer  a  little 
of  its  water  to  separate  tubes,  and  proceed  to  ascertain  (a) 
the  odor  of  the  water,  (b)  the  effect  of  adding  it  to  a  dilute 
solution  of  copper  chloride,  (c)  the  effect  of  adding  it  to  a 
dilute  solution  of  zinc  acetate. 

Compare  these  actions  of  the  water  with  the  actions  of 
the  gas  itself. 

End  the  Experiment.  —  Invert  each  flask  in  Avater ; 
remove  the  stopper,  and  leave  it  standing  for  some  hours. 

General The  effects  of  H2S  1  on  copper  chloride  and 

1  The  symbols  of  the  elements  in  a  compound  are  often  written 
instead  of  the  name  of  the  compound.  Thus,  H2S  stands  for  hydro- 


SULPHUR  AND   SOME  OF  ITS   COMPOUNDS.       53 

zinc  acetate  are  typical.  Similarly,  the  gas  or  its  solution 
will  convert  the  compounds  of  several  other  metals  into 
sulphides. 

II.     Sulphuric   Acid   and   Sulphates. 

EXPERIMENT   43. 

Object.  —  To  study  the  mutual  action  of  strong  sulphuric 
acid  and  water. 

Manipulation  and  Notes.  —  Into  a  wide-mouthed  bot- 
tle pour  40  cc.  of  cold  water.  Then  pour  into  it  gradually, 
while  you  stir  it,  40  cc.  of  strong  sulphuric  acid.  Feel  the 
sides  of  the  bottle  (note).  Insert  a  test  tube  holding  a  little 
alcohol  (note). 

General.  —  The  evolution  of  heat  is  evidence  of  chemical 
action. 

Sulphuric  acid  combines  readily  with  the  constituents  of 
water  whenever  the  two  liquids  are  brought  together. 

EXPERIMENT   44. 
Object.  —  To  study  the  action  of  sulphuric  acid  on  wood. 

Manipulation  and  Notes.  —  Put  2  or  3  cc.  of  strong 
acid  into  a  test  tube,  and  place  in  it  the  end  of  a  clean  pine 
stick.  After  a  few  minutes  rinse  the  stick  with  water  (note}. 
The  constituents  of  wood  are  chiefly  carbon,  hydrogen,  and 
oxygen.  In  the  light  of  Exp.  43,  how  would  you  explain 
the  change  in  the  wood?  Use  paper  instead  of  wood  (note). 

General.  —  These  results  are  typical.  All  organic  sub- 
stances are  affected  in  a  similar  way  by  this  acid. 

gen  sulphide,  because  hydrogen  (H)  and  sulphur  (S)  are  its  constitu- 
ents. The  small  figure  2  shows  that  there  are  two  combining  weights 
of  H  to  one  of  S.  Such  abbreviations  are  called  formulas.  See  list 
of  chemicals,  Appendix,  C,  2. 


54  LABORATORY   STUDIES  IN   CHEMISTRY. 

EXPERIMENT    45. 

Object.  —  To  study  the  action  of  sulphuric  acid  on  metals. 

Manipulation  and  Notes.  —  Put  a  small  piece  of  the 
given  metal  into  a  test  tube.  Cover  it  with  dilute  aeid. 
Close  the  tube  loosely  with  the  finger.  If  a  gas  is  set  free, 
test  it ;  but  if  no  action  begins  soon,  apply  a  gentle  heat 
(note).  If  still  there  is  no  action,  pour  off  the  dilute,  and 
add  a  little  concentrated  acid,  and  proceed  as  before  (note). 

When  the  action  is  ended,  filter,  evaporate  the  liquid, 
and  describe  the  substance  obtained. 

Use  magnesium  in  the  form  of  ribbon  or  wire.  Kepeat 
or  recall  the  results  of  Exps.  7  and  13  (c).  Do  not  breathe 
the  gases! 

General.  —  The  solids  obtained  by  action  of  sulphuric 
acid  on  the  metals  are  sulphates.  These  experiments  are 
typical. 

III.     Sulphur  Dioxide  and  Sulphites. 
EXPERIMENT   46. 

Object.  —  To  prepare  and  examine  the  gas  liberated  by 
action  of  sulphuric  acid  and  copper. 

Manipulation  and  Notes (a)  Setup  a  gas  apparatus, 

consisting  of  side-neck  flask,  three  collecting  flasks,  a,  b,  c, 
a  water  pan,  and  bottle.  The  connections  would  better  be  all 
glass.  Put  about  15  g.  of  copper  clippings  into  the  gen- 
erator ;  leave  a  empty ;  put  about  30  cc.  of  water  into  b,  and 
about  30  cc.  of  water  containing  about  2  g.  of  potassium 
hydroxide  into  c.  Then  connect  with  long  tubes  toward  the 
generator,  their  lower  ends  well  covered  with  water  in  the 
flasks. 

Prove  the  joints  to  be  air-tight.  Pour  about  25  cc.  of  strong 
sulphuric  acid  upon  the  copper,  and  close  the  generator. 


SULPHUR   AND   SOME   OF  ITS   COMPOUNDS.      55 

Apply  a  gentle  heat  until  the  action  is  well  started,  but  no 
longer.  Warm  again  if  the  action  slackens,  and  keep  a  slow 
and  steady  bubbling  of  gas  through  the  water  in  b.  When 
the  odor  of  the  gas  can  be  detected  at  c,  add  a  delivery  tube, 
and  collect  the  overflow  of  gas  by  displacement  of  water. 

Describe  and  explain  whatever  occurs  in  every  part  of 
the  apparatus,  and  draw  all  possible  inferences  about  the 
properties  of  the  gas. 

When  the  liquid  in  c  is  saturated  (how  known),  disconnect 
the  generator,  and  at  once  join  the  side  neck  to  the  short 
tube  of  an  empty  flask,  and  connect  the  long  tube  with  a  de- 
livery tube  inserted  in  a  strong  solution  of  sodium  hydrox- 
ide (give  reason).  Disconnect  all  the  flasks.  Then  proceed 
to  examine  the  gas. 

(b)  Determine  its  effect  on  fire  by  a  splinter  flame  in  the 
mouth  of  a.     The  stopper  should  be  at  once  replaced. 

(c)  Determine  the  behavior  of  its  solution  toward  litmus 
by  adding  to  litmus  solution  in  a  tube  a  small  portion  from 
b  without  removing  the  stopper.     Is  it  acid,  or  basic,  or 
neutral  ? 

(d)  Determine  its  effect  on  a  solution  of  logwood  by  add- 
ing a  portion  from  b  to  a  tube  containing  the  colored  liquid 
previously  made  by  boiling  a  few  chips  of  logwood  in  water. 

Try  its  action  on  other  colors.  Suspend  a  small  flower  or 
a  few  petals  in  a,  or  in  a  bottle  full  of  gas. 

(e)  Consider  what  chemical  action  may  have  occurred  in 
the  potassium  hydroxide.     Evaporate  the  saturated  solution 
of  the  gas  in  flask  c.    In  the  mean  time  invert  the  collecting 
flasks  with  open  mouths  under  water,  and  leave  standing 
(give  reason).     Is  the  residue  obtained  by  evaporation  the 
potassium   hydroxide  which    was  put  into  c?     Decide  by 
treating  it  with  a  little  hydrochloric  acid. 

General.  —  The  foregoing  experiments  have  revealed  the 
most  prominent  characteristics  of  sulphur  dioxide  (name 


56  LABORATORY  STUDIES  IN   CHEMISTRY. 

theiri)  ;  its  action  on  certain  coloring  matters,  which  renders 
it  useful  as  a  bleaching  agent  in  the  arts ;  and  its  chemical 
relations  to  water  and  bases  (explain).  The  salts  formed 
by  the  action  of  its  solution  on  hydroxides  are  sulphites. 

(/)  Judging  from  Exp.  18  and  the  definition  of  the 
term  salt,  what  salt  should  have  been  produced  by  the  sul- 
phuric acid  and  copper  in  the  foregoing  work?  Can  you 
see  any  indications  of  this  salt  in  the  side-neck  flask  ?  To 
test  this  supposition,  proceed  to  examine  the  residue  in  the 
flask,  as  follows  :  — 

Decant  the  liquid  from  the  flask,  leaving  all  solid  residue 
behind.  Put  about  50  cc.  of  water  into  the  flask,  shake  it 
well,  and  let  it  stand  awhile  (note).  Finally  filter;  evap- 
orate the  filtrate  to  crystallization ;  let  stand  for  crystals 
to  form.  Decant  the  liquid,  dry  the  crystals  by  contact 
with  filter  paper,  and  decide  whether  they  are  the  salt  you 
predicted. 

IV.    Comparison  of  Sulphides,  Sulphites,  and  Sulphates. 

EXPERIMENT   47. 

Object.  —  To  study  the  action  of  dilute  adds  on  sulphides, 
sulphites,  and  sulphates. 

Manipulation  and  Notes.  —  (a)  Put  a  little  of  the 
powder  of  some  specimen  of  each  of  these  compounds  into 
a  separate  tube,  moisten  it  with  water,  and  add  a  little 
dilute  hydrochloric  acid.  Watch  for  effervescence,  and  any 
other  evidence  of  chemical  action.  Notice  the  odor  of  any 
gas  which  may  be  set  free.  If  no  action  begins  soon,  heat 
may  be  used  (note). 

(b)  Use  dilute  sulphuric  acid,  making  the  experiments  in 
the  same  way  (note). 

Point  out  the  difference  in  the  behavior  of  these  three 
classes  of  compounds  toward  the  dilute  acids  used. 


SULPHUR  AND   SOME  OF  ITS   COMPOUNDS.       57 

EXPERIMENT   48. 

Object.  —  To  study  the   action  of  barium  chloride  on  sul- 
phites and  sulphates. 

Manipulation  and  Notes.  —  (a)  Add  drops  of  barium 
chloride  to  a  solution  of  a  sulphite  and  to  a  solution  of  a 
sulphate.  Then  compare  the  precipitates  which  appear. 

(&)  Learn,  by  experiment,  whether  these  two  precipitates 
are  alike  soluble  in  hydrochloric  acid. 

(c)  See  whether  both  these  precipitates  will  appear  if  you 
add  the  hydrochloric  acid  to  the  solutions  before  you  add 
the  barium  chloride. 

Point  out  the  resemblance  in  the  behavior  of  these  two 
classes  of  compounds  toward  barium  chloride.  State  clearly 
the  condition  in  which  their  behavior  toward  barium  chloride 
differs. 

From  the  foregoing  experiments  one  may  make  a  plan  by 
which  to  decide  whether  a  given  substance  is  a  sulphide,  or 
a  sulphite,  or  a  sulphate.  Try  to  do  this. 

For  practice,  take  from  the  teacher,  or  a  friend  who 
knows  what  they  are,  a  few  substances,  and  see  if  you 
can  decide  whether  each  is  a  sulphide,  or  a  sulphite,  or  a 
sulphate. 


58          LABORATORY  STUDIES   IN  CHEMISTRY. 


IX.     NITROGEN. 


EXPERIMENT   49. 

Object.  —  To  obtain  nitrogen  by  burning  the  oxygen  out  of 
air  with  sulphur. 

Manipulation  and  Notes.  — Cut  a  slice  half  an  inch 
thick  from  a  cork  which  is  much  smaller  than  the  mouth  of 
a  bottle.     Shape  the  top  of  the  cork 
into   a   shallow   cup,  and   cover   it 
with  a  paste  of  moistened  plaster  of 
Paris.     Let  the  plaster  become  diy, 
then  put  sulphur  in  this  cup,  place 
it  on  the  shallow  water  in  a  water 
pan,  set  fire  to  the  sulphur,  and  put 
Fig.  20.  the  bottle   bottom  upward  over  it, 

as  shown  in  Fig.  20.     Describe  the 

name  of  the  sulphur,  the  action  of  the  water  when  the 
burning  is  over,  the  change  in  the  gas  after  long  time 
standing.  The  gas  obtained  at  last  is  nitrogen. 

EXPERIMENT   5O. 

Object.  —  To  obtain   nitrogen  by  burning  the  oxygen  out  of 
air  with  phosphorus. 

Manipulation  and  Notes.  —  Follow  the  directions  given 
above  for  burning  sulphur,  but  use  a  piece  of  phosphorus 
not  larger  than  a  good-sized  kernel  of  wheat,  with  a  smaller 
bottle  holding  about  200  cc.,  and  observe  the  following 
precautions. 

Precautions.  —  The  handling  of  phosphorus  is  dangerous 
unless  it  is  done  with  great  care.  Phosphorus  takes  fire 


NITROGEN.  69 

easily,  and  burns  the  flesh  cruelly.  Therefore  cut  it  under 
water,  lift  the  piece  with  the  knife  blade,  dry  it  by  gentle 
contact  with  filter  paper,  and  put  it  into  a  dry  cup.  Never 
handle  phosphorus  without  using  the  greatest  care.  Red 
phosphorus  may  be  used  with  less  danger  than  the  common 
yellow  variety. 

Set  tire  to  the  phosphorus  by  touching  it  with  a  warm 
wire  (note). 

Let  the  bottle  stand  until  its  contents  become  colorless 
(explain). 

EXPERIMENT   51. 
Object. —  To  discover  the  properties  of  nitrogen. 

Manipulation  and  Notes.  —  (a)  What  is  the  color  of 
this  gas  ? 

(b)  What  is  its  action  with  a  burning  splinter  ?     Slip  a 
square  of  glass  or  of  cardboard  under  the  mouth  of  a  bottle 
containing  the  gas,  lift  it  out  of  the  water,  turn  it  mouth 
upward,  stand  it  on  the  table,  and  leave  it  covered.     At 
once  ignite  a  splinter  of  wood,  uncover  the  bottle,  and  in- 
sert the  flame  just  inside  its  mouth.     Leave  the  bottle  un- 
covered.    Treat  the  other  bottle  of  gas  in  the  same  way. 
Leave  this  bottle  also  uncovered. 

(c)  Is  it  heavier,  or  lighter,  than  air  ?     The  bottles  hav- 
ing now  stood  some  minutes  uncovered,  again  insert  a  flame 
into  the  bottle  first  left  uncovered,  and  afterward  into  the 
other. 

Tests.  —  How  would  you  decide  whether  a  given  color- 
less gas  is  nitrogen,  or  hydrogen,  or  oxygen  ? 


60          LABORATORY  STUDIES  I#  CHEMISTRY. 


X.     ANALYSIS   OF   AIR. 


EXPERIMENT   52. 

Object.  —  To  determine  approximately  the  relative  propor- 
tion of  oxygen  to  other  constituents  of  air. 

Manipulation  and  Notes.  —  Support  a  glass  tube  15 
to  30  cm.  long  and  about  2  cm.  wide,  and  closed  at  one  end, 
so  that  it  will  stand  with  its  open  end  under  water  in  a 
water  pan.  Cut  from  small  copper  wire  a  piece  about  two 
thirds  the  length  of  the  tube.  Cut  from  a  stick  of  phos- 
phorus a  piece  about  as  large  as  a  bean  of  medium  size. 
Press  the  end  of  the  wire  (under  water)  into  this.  Thrust 
the  phosphorus  end  of  the  wire  up  into  the  glass  tube,  and 
bring  the  mouth  of  the  tube  down  again  at  once  into  the 
water.  Notice  whether  any  action  sets  in.  Let  the  action 
go  on  until  it  ends :  it  will  require  several  hours,  perhaps 
until  next  day. 

Then  note  any  changes.  Mark  the  level  of  the  water  in 
the  tube  by  a  rubber  band  or  a  thread. 

Cover  the  mouth  of  the  tube  closely  with  the  thumb. 
Lift  it  and  turn  its  mouth  upward,  letting  no  air  enter, 
and  test  the  gas  within  by  a  lighted  splinter.  What  is  the 
result  ?  Decide  what  the  phosphorus  has  taken  out,  and 
what  is  left. 

Find  the  volume  of  the  gas  that  was  left  by  measuring 
the  water  required  to  fill  the  tube  up  to  the  rubber  band. 
Find  the  volume  of  the  air  which  was  used  by  measuring 
the  water  required  to  till  the  tube.  Find  the  volume  of 


> 
ANALYSIS   W  AlE*    ' 


CM  %K     f:  -     ;v  - 

BE  SIT 


the  gas  absorbed   by  taking  the 
thus : — 


results 


cc. 
cc. 
cc. 


Volume  of  air  used 

Volume  of  oxygen  absorbed 

Volume  of  nitrogen  and  other  gases    = 

What  fractional  part  of  the  air  is  oxygen  ? 

What  fractional  part  of  the  air  is  nitrogen  and  other  gases  ? 

How  many  cubic  centimeters  of  oxygen  in  100  cc.  of  air  ? 


EXPERIMENT    53. 

Object.  —  To  find  out  how  many  cubic  centimeters  of  nitro- 
gen, and  how  many  of  oxyyen  and  carbon  dioxide,  there 
are  in  100  cc.  of  air. 

Plan.  —  To  do  this,  we  will  imprison  a  vesselful  of  air, 
and  then  run  into  it  a  liquid  which  will  absorb  both  the 
oxygen  and  the  carbon  dioxide  completely,  and  leave  the 
nitrogen.  We  can  then  measure  the  nitrogen  which  is  left, 
and  we  can  find  out  how  much  there  was  of  the  other  two 
by  measuring  the  liquid  which  has  gone  into  the  tube  to 
take  their  place. 

The  Apparatus.  —  Take  a  test  tube  (t,  Fig.  21)  to  hold 
the  air.  A  6-inch  tube,  f  of  an  inch  in  diame- 
ter, will  do ;  an  8-inch  tube  of  the  same  diameter 
is  better.  The  rubber  stopper  c  is  so  large,  that 
its  small  end  will  enter  the  tube  only  about  a 
half  inch.  It  has  two  holes.  To  close  one,  use 
a  solid  rod  of  glass,  s  ;  into  the  other  put  a  glass 
tube  reaching  just  a  very  little  below  the  cork, 
as  shown.  A  piece  of  thin  rubber  tubing,  h,  is 
cut  about  6  inches  long.  There  is  a  pinchcock, 
p,  by  which  its  walls  may  be  pinched  so  as  to 
close  it  completely.  F  is  a  small  glass  funnel.  F'ff-  21- 

Stretch  the  lower  end  of  h  over  the  tube  in  the  cork  c, 


LABORATORY  STUDIES  IN   CHEMISTRY. 


Fig.  22. 


and  fix  its  upper  end  over  the  stem  of  F.     Then  place  the 

funnel  in  the  clamp  of  the  support,  as  shown  in  Fig.  22,  and 
remove  the  rod  s. 

The  Liquid.  —  To  absorb  the  oxy- 
gen and  carbon  dioxide  gases,  use  a 
mixture  of  pyrogallic  acid  and  potas- 
sium hydroxide. 

Take  a  small  teaspoonful  of  the 
solid  acid  and  add  10  cc.  of  water : 
it  will  soon  dissolve.  To  this  add 
5  cc.  of  strong  solution  of  potassium 
hydroxide,  and  at  once  pour  it  into 
the  funnel.  Next  hold  the  dish  be- 
low the  cork  and  open  the  pinchcock 
j)  a  moment,  to  let  the  liquid  run 
down  and  fill  the  tubes  completely. 

Carefully  take  off  the  drop,  which  hangs  at  the  lower  end 

of  the  tube  below  the  cork,  with  a  piece 

of  filter  paper. 

The  Air.  —  Press  the  tube  t  up  over 

the   cork,  as  seen  in  Fig.  23,  until  the 

joint  is  air-tight,  and  after  a  minute  put 

the  rod  s  into  the  open  hole  of  the  cork. 

You  have  now   imprisoned  a  tubeful  of 

air;    none  can  get  out,  and  no  more  can 

get  in. 

The  hole  in  the  cork  was  left  open,  be- 
cause, if  it  were  not  open,  the  pressure 

of  the  cork  would  crowd  the  air  below, 

and   there   would    be    too   much   in   the 

tube ;    and  then,  too,  handling  the  tube 

warms     it,     and    the     volume      of     air 

changes  with   heat.     With   the  hole  open,  the  air  in  the 

tube  soon  comes  to  be  just   as  warm   and   just    as    much 


Fig.  23. 


ANALYSIS   OF  AIR. 


63 


pressed  as  the  air  outside.  Whenever  a  gas  of  any  kind  is 
to  be  measured,  its  temperature  and  pressure  must  be  the 
same  as  those  of  the  air  outside. 

The  Absorption. — Now  press  the     (  j 
pinchcock  p;  a   little  stream  of  the 
liquid  falls  into  t  at  once,  and  then 
drops  follow,  or,  if  the  tube  be  slightly     £ 
inclined,  a  slender  stream  will  flow 
down  its  side.    It  will  continue  to  enter 
as  long  as  there  is  any  oxygen  or  car- 
bon dioxide  for  it  to  absorb,  and  then 
stop.     Close  the  pinchcock.     The  gas 
which  is  left  in  the  tube  is  nitrogen. 

But  this  gas  is  crowded  down  by  the 
pressure  of  the  liquid  in  the  rubber 
tube  and  funnel  above  ;  and  to  relieve 
it  from  this  pressure  take  hold  of  the 
cork  c,  and  the  rim  of  t,  so  as  not  to 
warm  the  gas  with  the  hand,  and  lift  the  tube,  bottom  up, 
as  shown  at  T  in  Fig.  24,  making  the  level  of  the  liquid 
the  same  in  the  tube  and  in  the  funnel.  Then  open  the 
pinchcock.  Some  of  the  liquid  will  run  out  of  T.  When 
the  liquid  stands  at  the  same  level  in  the  tube  and  in  the 
funnel,  close  the  cock  and  bring  the  tube  down  again. 

The  almost  black  liquid  in  t  has  now  taken  out  all  the 
oxygen  and  carbon  dioxide  from  the  tubeful  of  air,  and  left 
all  its  nitrogen. 

The  Measuring.  —  Measure  the  liquid  in  the  tube  to 
find  how  much  oxygen  was  taken  out,1  and  the  space  above 
it  to  find  how  much  nitrogen  was  left. 

To  do  this,   slip  two  small  rubber  rings  over  the  tube, 

1  And  carbon  dioxide  also.  But  the  volume  of  the  carbon  dioxide, 
in  so  small  a  quantity  of  air  as  we  use  in  this  experiment,  is  so  little 
that  we  may  leave  it  out  of  account. 


Fig.  24. 


64          LABORATORY  STUDIES   IN   CHEMISTRY. 

and  make  the  upper  edge  of  one  mark  th'e  place  of  the 
lower  end  of  the  cork ;  and  of  the  other,  the  top  of  the 
liquid.  These  rings  must  not  afterward  be  disturbed. 

Now  remove  the  cork,  empty  the  tube,  rinse  it  with 
water,  and  then  let  the  last  drop  of  water  drain  away. 
Finally,  with  a  graduated  cylinder,  find  out  exactly  how 
many  cubic  centimeters  of  water  will  fill  the  tube  to  the 
first  ring;  also  how  many  cubic  centimeters  will  fill  the 
tube  from  the  first  to  the  second  ring. 

The  Calculations.  —  From  these  two  numbers  we  can 
find  what  part  of  the  air  is  nitrogen,  and  what  part  is 
oxygen :  for  by  their  help  we  can  answer  the  following 
questions,  in  their  order,  one  after  another,  as  shown  by  an 
example  below. 

How  many  cubic  centimeters  of  air  were  in  the  tube  at  first  ? 

How  many  cubic  centimeters  of  nitrogen  did  this  air  yield  ? 

How  many  cubic  centimeters  of  oxygen  did  the  same  air 
yield  ? 

Then  what  fractional  part  of  the  air  is  nitrogen  ? 

What  fractional  part  of  the  air  is  oxygen  ? 

How  many  cubic  centimeters  of  nitrogen  in  100  cc.  of  air  ? 

How  many  cubic  centimeters  of  oxygen  in  100  cc.  of  air  ? 

An  Example.  —  In  an  actual  experiment  it  was  found  to 
take  of 

Water  to  fill  the  tube  to  the  first  ring 6.0  cc. 

Water  to  fill  the  tube  from  the  first  to  second  ring  .  .  .  23.5  cc. 

Hence  the  number  of  cc.  of  air  taken 29.5  cc. 

The  number  of  cc.  of  nitrogen  found 23.5  cc. 

The  number  of  cc.  of  oxygen  found 0.0  cc. 

Now,  this  would  show  plainly  that  |-|f  of  the  air  is  nitro- 
gen, and  g-fc  °f  ifc  ig  oxygen.  Then  in  100  cc.  of  air  there 

would  be 

Nitrogen 79.66  cc. 

Oxygen 20.34  cc. 


AMMONIA, 


65 


XL     AMMONIA:   THE   COMPOUND   OF  NITROGEN 
AND   HYDROGEN. 


EXPERIMENT   54. 

Object.  —  To  obtain  ammonia  gas  in  small  quantity. 

Manipulation  and  Notes.  —  Powder  a  very  little  am- 
monium chloride  and  also  a  little 
good  quicklime.  Then  mix  them 
well,  and  put  into  a  clean  and  dry 
test  tube  enough  to  half  fill  the 
rounded  bottom.  Take  the  tube 
between  the  fingers,  with  the  thumb 
over  its  mouth,  leaving  a  small  open- 
ing at  the  lower  edge,  and  hold  it 
some  time  in  the  hot  air  above  the 
flame,  a  little  inclined,  as  shown  in 
Fig.  25  (note). 

Present  a  rod  moistened  with  hydrochloric  acid  to  the 
mouth  of  the  tube. 

Take  the  odor  of  the  gas. 

Introduce  a  strip  of  moist  reddened  litmus  paper. 

EXPERIMENT   55. 

Object.  —  To  obtain  ammonia  gas  in  larger  quantity. 

Method.  —  Decompose  ammonium  chloride  by  slaked 
lime,  and  collect  by  displacement  of  air. 

Manipulation  and  Notes.  —  Set  up  three  dry  flasks,  a, 
b,  c,  with  all  glass  connections  (Fig.  8,  p.  20),  with  their 
short  tubes  toward  the  generator  (a  side-neck  flask),  and 


Fig.  25. 


66          LABORATORY  STUDIES  IN   CHEMISTRY. 

join  the  long  tube  of  c  to  a  tube  leading  to  the  bottom 
of  a  bottle  containing  a  very  little  water. 

Mix  thoroughly  about  25  g.  of  powdered  ammonium 
chloride  with  twice  as  much  recently  slaked  lime  in  fine 
dry  powder,  and  transfer  to  the  generator.  Heat  Avith  a 
very  low  flame.  When  the  ammonia  has  driven  the  air  all 
out  of  the  receivers  (decide  by  a  rod  wet  with  hydrochloric 
acid),  lift  the  tube  out  of  the  bottle  ;  twist  its  opened  end 
upward  ;  lower  an  inverted  flask  as  far  as  possible  over  it, 
and  fill  this  flask  by  displacement  of  air  (explain).  When 
the  flask  is  filled,  close  it  with  a  stopper,  and  stand  it  mouth 
down  on  the  table.  Disconnect  the  tube  from  flask  c,  and 
withdraw  the  heat. 

EXPERIMENT    56. 

Object. —  To  discover  properties  of  ammonia. 

Manipulation  and  Notes.  —  (a)  What  is  its  appear- 
ance ?  Note  its  odor.  Is  it  heavier,  or  lighter,  than  air  ? 

(b)  Is  it  soluble  in  water  ?     Take  the  flask  which  you 
filled  by  upward  displacement  of  air ;  bring  its  mouth  near 
the   surface  of  water  in   a  pan;    remove   the   stopper  and 
lower  the  mouth  of  the  flask  into  the  water. 

Remove  the  flask  with  its  contents,  and  place  it  on  the  table. 

(c)  What  is  its  action  on  contact  with  flame  ?     Discon- 
nect flask  c  ;  invert  it ;  remove  its  stopper ;  insert  the  flame 
of  a  taper. 

(d)  What  is  its  action  on  litmus  ?     Moisten  two  narrow 
strips  of  blue  litmus  paper.     Redden  one  of  them  by  hold- 
ing it  in  the  mouth   of   a  bottle   containing  hydrochloric 
acid.     Disconnect  flask  b.     Open  it,  and  at  once  insert  the 
two  papers.     Describe  effects.     Is  ammonia  an  acid,  a  basic, 
or  a  neutral  substance  ? 

(e)  Is  this  character  shown   by  a  solution  of  the  gas  ? 
Introduce  a  strip  of  reddened  litmus  paper  into  the  solution 


AMMONIA.  67 

in  flask  c.  Or  redden  some  blue  litmus  water  with  as  little 
hydrochloric  acid  as  will  do  it,  and  then  pour  into  it  some 
of  the  water  which  dissolved  the  gas  in  c. 

Prepare  a  deep  evaporating  dish  nearly  full  of  reddened 
litmus  water.  Disconnect  flask  a.  Invert  it.  Lower  it 
nearly  to  the  surface  of  the  water.  Remove  its  stopper,  and 
press  its  mouth  nearly  to  the  bottom  of  the  water.  De- 
scribe and  explain. 

Tests.  —  How  would  you  decide  whether  a  given  color- 
less gas  is  ammonia  ? 

EXPERIMENT    57. 

Object —  To  obtain  ammonia  from  ammonium  hydroxide. 

Manipulation  and  Notes.  —  Arrange  the  apparatus  as 
in  Fig.  2(1  Put  10  or  15  cc. 
of  the  ammonium  hydroxide 
into  the  side-neck  flask,  close 
its  mouth,  and  connect  it  with 
the  short  tube  of  the  flask  a,  as 
shown.  Now  make  the  lamp 
flame  very  small,  so  that  only 
a  current  of  hot  air  will  warm 
the  liquid  in  the  flask. 

The  gas  obtained  may  be  used 
for  the  purpose  of  studying  the 
properties,  as  described  in  Exp.  56.  Fia-  26- 

What  is  the  difference  between  ammonia  and  ammonium 
hydroxide  ? 

EXPERIMENT   58. 

Object.  —  To  study  the  action  of  ammonium  salts  with  po- 
tassium hydroxide. 

Manipulation  and  Notes.  —  Put  a  little  solid  ammo- 
nium chloride  into  a  test  tube.  Moisten  it  with  drops  of 
potassium  hydroxide,  and  heat  it  gently. 


68  LABORATORY   STUDIES  IN   CHEMISTRY. 

Examine  the  gas  which  is  set  free,  (a)  for  odor,  (//)  with 
reddened  litmus  paper,  (c)  with  hydrochloric  acid  on  a 
glass  rod. 

Repeat  the  work,  using  ammonium  sulphate,  and  again 
with  ammonium  carbonate. 

Test.  —  How  would  you  decide  whether  a  given  solid  is 
a  salt  of  ammonium  ? 

EXPERIMENT    59. 

Object.  —  To  ascertain  the  effect  of  heat  on  some  ammonium 
salts. 

Manipulation  and  Notes.  —  Place  a  small  quantity  of 
the  given  salt  in  the  bottom  of  a  dry  test  tube.  Apply  heat 
gradually.  Keep  the  upper  part  of  the  tube  cold,  and  its 
mouth  loosely  closed  with  the  finger. 

Use  (a)  ammonium  chloride,  (b)  ammonium  carbonate,  (c) 
ammonium  nitrate.  Test  for  gas  in  the  tube,  above  the 
nitrate. 

General.  —  Many  salts  of  ammonium,  like  the  chloride 
and  the  carbonate  in  these  experiments,  are  vaporized  with- 
out chemical  change,  by  heat.  Many  others,  like  the 
nitrate,  are  decomposed  by  heat. 


NITRIC  ACID,   NITROGEN   OXIDES,   NITRATES.    09 


XII.    NITRIC    ACID,   NITROGEN   OXIDES, 
NITRATES. 


EXPERIMENT   6O. 

Object. — Is  the  action  of  nitric  acid  on  metals  similar  to 
that  of  sulphuric  acid  ? 

Manipulation  and  Notes.  —  Put  a  small  piece  of  zinc 
into  a  test  tube,  and  add  0  or  8  drops  of  nitric  acid  (note). 

Recall  the  action  of  zinc  on  sulphuric  acid  (Exp.  7),  or  put 
a  small  piece  of  zinc  in  a  test  tube ;  cover  it  with  dilute 
sulphuric  acid,  and  test  the  gas. 

Use  a  clipping  of  copper  with  nitric  acid,  and  decide 
whether  the  action  is  the  same  as  with  zinc. 

EXPERIMENT   61. 

Object.  —  To  study  the  mutual  action  of  nitric  acid  and 
copper. 

Manipulation  and  Notes.  —  («.)  Fit  up  the  apparatus 
for  making  and  collecting  gases  heavier  than  air  (Fig.  8, 
p.  20),  using  flasks  a,  b,  c.  Put  water  into  both  a  and  b, 
but  none  in  c.  After  the  connections  are  made,  put  about 
7  g.  of  small  pieces  of  copper  into  the  side-neck  flask, 
pour  in  about  40  cc.  of  dilute  nitric  acid  (half  water),  and 
close  the  flask  with  its  air-tight  stopper  (note).  Is  there 
any  evidence  that  more  than  one  kind  of  gas  is  produced  ? 

(b)  When  the  flask  c  is  filled,  disconnect  c,  attach  a  de- 
livery tube  to  b,  and  proceed  to  collect  the  gas  in  a  bottle 
by  displacement  of  water.  When  the  bottle  is  half  full  of 
gas,  remove  the  tube  from  the  water,  disconnect  the  gener- 


70          LABOR ATOliY  STUDIES  IN   CHEMISTRY. 

ator,  and  pour  the  liquid  from  it  into  an  evaporating  dish. 
Stand  the  dish,  also  the  generator,  aside  until  the  end  of  the 
experiment. 

(c)  Proceed  to  examine  the  gases.     Remove  the  stopper 
from  c  carefully,  pour  in  gently  a  few  cubic  centimeters  of 
water,  and  return  the  stopper  to  its  place.     Close  the  ends 
of  both  glass  tubes ;  lift  the  flask  and  shake  it  well  (note). 

(d)  Keep  the  tub?s  tightly  closed  while  you  immerse  the 
mouth  of  the  flask  in  water,  then  open  them  (note). 

(e)  Invert   flask    b,  and    let    the   water   run    out  of   the 
short  tube.     What  must  enter  at  the  same  time  ?     Describe 
result,  and  account  for  it.     Treat  with  water  as  you  treated  c. 

(f)  Lift   the    bottle  just  enough   to  let  bubbles    of   air 
enter  (note).     Slip  a  glass  plate  under  its  mouth,  lift  and 
shake  the  bottle   (note).      Repeat   these   operations.     How 
can  these  observed  changes  be  explained  ? 

((/)  Very  carefully  open  flask  «,  and  insert  a  burning 
splinter  (note). 

End  the  Experiment.  —  Filter  the  liquid  which  came 
from  the  generator,  and  allow  it  to  stand  to  evaporate. 
Put  water  in  the  generator,  replace  the  stopper,  cover  the 
side  neck,  shake,  and  invert  the  side  neck  in  water.  Ex- 
amine the  residue  in  the  dish  after  evaporation  (note). 

EXPERIMENT    62. 

Object. —  To  discover  if  the  action  with  zinc  is  the  same 
whether  the  acid  is  concentrated  or  dilute. 

Manipulation  and  Notes.  —  Make  dilute  nitric  acid  (1 
of  acid  to  4  of  water),  and  pour  about  5  cc.  upon  a  piece  of 
zinc  in  a  test  tube.  Keep  it  cool,  and  let  it  stand,  loosely 
covered.  Examine  the  gas  liberated,  comparing  it  with  that 
obtained  when  the  concentrated  acid  was  used  in  Exp.  61, 
and  with  that  given  off  by  zinc  and  dilute  sulphuric  acid. 


NITRIC  ACID,   NITROGEN   OXIDES,   NITRATES.    71 
EXPERIMENT  63. 

Object.  —  To  collect  and  examine  the  gas  which  zinc  liber- 
ates from  cold  dilute  nitric  acid. 

Manipulation  and  Notes Arrange  a  side-neck  flask 

with  delivery  tube,  water  pan,  and  bottle,  to  collect  the  gas 
by  displacement  of  water  (Fig.  11,  p.  22).  Dilute  25  cc.  of 
nitric  acid  with  100  cc.  of  water.  Put  several  pieces  of  zinc 
into  the  generator,  and  when  the  acid  is  cold  pour  it  upon 
the  zinc.  Close  the  flask,  wait  a  full  minute,  and  then  pro- 
ceed at  once  to  collect  the  gas.  The  generator  should  be 
kept  cool ;  it  may  very  well  be  supported  in  a  dish  of  cold 
water.  Finally  take  the  tube  from  the  water,  and  then  test 
the  gas  with  air  and  with  flame. 

Does  it  change  by  contact  with  air?  Lift  the  bottle 
enough  to  let  bubbles  of  air  enter  (note). 

How  does  it  act  with  flame  ?  Open  the  generator,  and 
apply  the  flame  test  in  the  usual  Avay. 

General.  —  There  are  several  compounds  of  nitrogen  and 
oxygen.  One  is  a  colorless  gas  which  promotes  combustion, 
called  nitrous  oxide  ;  another  is  a  colorless  gas  which  extin- 
guishes a  taper  flame,  called  nitric  oxide  ;  while  another  is 
a  red-brown  gas,  called  nitrogen  peroxide. 

What  gas  is  set  free  when  zinc  or  copper  acts  on  moder- 
ately strong  nitric  acid  ?  What  other  gas  is  produced  when 
this  one  mixes  with  air  (or  oxygen)  ? 

What  gas  is  set  free  when  zinc  acts  on  cold  dilute  nitric 
acid  ? 

EXPERIMENT    64. 

Object.  —  To  study  the  action  of  zinc  on  very  dilute  nitric 

acid  in  presence  of  sulphuric  acid. 

Manipulation  and  Notes.  —  Dilute  1  ec.  of  sulphuric 
acid  with  5  cc.  of  water,  and  when  cold  pour  it  upon  zinc 
in  a  test  tube.  Keep  it  cold  by  inserting  it  in  cold  water. 


72         LABORATORY  STUDIES  IN   CHEMISTRY. 

Test  the  gas.  Add  drop  by  drop  a  mixture  of  1  cc.  of  nitric 
acid  with  3  cc.  of  water,  and  observe  its  effect  on  the  rapid- 
ity of  the  effervescence.  Add  the  nitric  acid  until  the  effer- 
vescence ceases.  Then  let  the  tube  stand  for  some  hours. 

Filter,  and  evaporate  the  liquid  nearly  to  dry  ness.  Trans- 
fer to  a  test  tube,  add  drops  of  potassium  hydroxide,  and 
warm  the  mixture.  Then  test  for  odor,  also  with  reddened 
litmus  paper,  also  with  hydrochloric  acid  on  a  glass  rod,  and 
decide  what  substance  is  liberated. 

General.  —  The  foregoing  experiments  show  that  the 
chemical  action  of  zinc  and  nitric  acid  depends  on  tem- 
perature and  the  strength  of  the  acid.  In  many  other 
cases,  as  in  this,  the  same  substances  yield  different  prod- 
ucts, according  to  the  conditions  of  the  experiment. 

EXPERIMENT   65. 

Object.  —  To  learn  the  effect  of  lieat  on  some  nitrates. 

Manipulation  and  Notes.  —  1'lace  a  small  quantity  of 
the  given  nitrate  in  a  dry  test  tube.  Heat  gradually.  Ex- 
amine the  gas  produced,  and  describe  the  effect  of  the  heat. 

Use  (a)  lead  nitrate, 
(1}  copper  nitrate,  (c) 
ammonium  nitrate,  or 
recall  Exp.  59. 

EXPERIMENT   66. 

Object.  —  To  obtain  ni- 
trous oxide  l)ij  heating 
a  in  monium  n  itra  te. 
Manipulation  and 
Notes.  —  Put  from  7 
to  10  g.  of  ammonium 
nitrate  into  the  side-neck  flask,  which  should  be  dry,  and 
join  the  flasks,  a,  b,  c,  as  usual  for  heavy  gas.  To  condense 


NITRIC  ACID,   NITROGEN   OXIDES,    NITRATES.    73 

steam,  put  the  empty  flask  a  into  a  dish  of  cold  water  (ice- 
water  is  best).  It  may  be  made  to  stand  firmly  in  the  water 
by  a  clamp.  "Use  the  gentle  heat  of  a  small  flame,  only  just 
hot  enough  to  melt  and  keep  the  nitrate  bubbling. 

What  is  the  color  of  nitrous  oxide  ?     Its  odor  ? 

Test  it  in  b  with  a  spark  on  the  end  of  a  splinter.  Leave 
c  open  for  two  or  three  minutes,  and  then  test  with  a 
glowing  splinter  (note). 

EXPERIMENT   67. 

Object.  —  To  study  the  effect  of  nitric  acid  on  ferrous  sul- 
phate, sometimes  called  "  copperas." 

Manipulation  and  Notes.  —  (a)  Into  a  little  dilute 
nitric  acid  in  a  test  tube  drop  a  good  crystal  of  the  ferrous 
sulphate.  Do  not  shake  it.  Describe  the  color  which  soon 
appears  in  the  liquid  around  the  crystal. 

(/>)  Put  1  drop  of  strong  acid  into  5  cc.  of  water,  and 
repeat  the  work  with  this  very  dilute  acid. 

(c)  Try  the  solution  of  a  nitrate,  instead  of  nitric  acid, 
in  the  same  way.     If  you  do  not  get  the  same  result,  there 
is  probably  little  or  no  free  nitric  acid  present. 

(d)  Mix  a  little  solution  of  the  nitrate  with  a  solution 
of  the  ferrous  sulphate,  incline  the  tube,  and   let  a  little 
concentrated    sulphuric    acid    run   down   the   inside  of  the 
glass  to  the  bottom.     Do  not  shake  it.     Observe  the  effect 
where  the  two  liquids  are  in  contact. 

(e)  Make  the  experiment  again  with  the  nitrate  and  acid, 
but  add  the  ferrous   sulphate  to  the  liquid  when  hot. 

Test.  —  How  would  you  decide  whether  a  given  liquid 
contains  free  nitric  acid  ? 

How  would  you  decide  whether  a  given  solid  is  a  nitrate  ? 

Get  a  little  of  some  white  solid  from  the  teacher,  or  a 
friend  who  knows  what  it  is,  and  see  if  you  can  tell  by  the 
copperas  test  whether  it  is  a  nitrate. 


74          LABORATORY  STUDIES  IN   CHEMISTRY. 


XIII.     CARBON,   CARBON   DIOXIDE, 
CARBONATES. 


EXPERIMENT   68. 

Object.  —  To  convert  wood  into  charcoal. 

Manipulation  and  Notes.  —  Break  the  head  from  a 
match,  and  drop  the  body  into  a  test  tube.  Then  heat  it 
slowly  by  holding  the  tube  almost  horizontally  just  above 
the  tip  of  a  lamp  flame,  and  move  the  tube  back  and  forth 
to  heat  the  length  of  the  wood.  Describe  all  the  products 
you  can  discover,  noting  particularly  if  vapors  go  off  as 
gases,  or  condense  into  liquids.  Compare  the  solid  residue 
with  a  piece  of  soft-wood  charcoal. 

General.  —  This  experiment  illustrates  the  action  in- 
volved in  charcoal  making. 

EXPERIMENT   69. 

Object.  —  To   examine   the   action   of   carbon   on    coloring 
substances. 

Manipulation  and  Notes.  —  (a)  Prepare  a  filter,  and 
rest  the  funnel  in  the  mouth  of  a  cylinder.  Fill  the  filter 
nearly  full  of  boneblack.  Finally  pour  upon  it  some  water 
colored  with  blue  litmus.  If  it  comes  through  still  colored, 
pour  it  back,  and  let  it  run  through  a  second  time.  Run  it 
through  a  third  time,  if  you  think  it  best  to  do  so  (note). 

(b)  In    the    same    way    filter   some    water   colored    with 
cochineal  (note}. 

(c)  Try  a  solution  of  dark-brown  sugar  (note). 


CARBON,    CARBON  DIOXIDE,    CARBONATES.      75 


(d)  Try  a  solution  of  potassium  chromate.  This  is  a 
mineral  coloring  matter ;  the  others  have  been  organic. 

General.  —  These  experiments  reveal  the  power  of  cer- 
tain forms  of  carbon  us  an  absorbent,  and  illustrate  its  use 
as  a  iilter  for  purifying  water  and  refining  sugar. 

EXPERIMENT   7O. 
Object.  —  To  study  tlie  action  of  carbon  on  copper  oxide. 

Manipulation  and  Notes.  —  Make  a  mixture  of  1  g.  of 
copper  oxide  with  about  its  own  bulk  of  powdered  char- 
coal. Put  it  into  the 
side  -  neck  ignition 
tube,  and  place  the 
end  of  the  delivery 
tube  in  some  lime- 
water  contained  in  a 
test  tube,  as  shown 
in  Fig.  28,  and  then 
apply  the  heat  of  the 
Bunsen  lamp. 

From  the  effect  on 
the  limewater  you  rec- 
ognize the  product  of  Fig'  28' 
the  action.     From  the  residue  in  the  tube  you  can  judge  the 
change  in  the  oxide.     You  can  then  explain  the  action. 

General.  —  This  experiment  reveals  the  power  of  carbon 
as  a  "  reducing  agent,"  which  is  applied  in  metallurgy  to 
obtain  metals  from  their  ores. 

EXPERIMENT   71. 

Object.  —  To  obtain  carbon  dioxide  and  discover  its  prop- 
erties. 

Manipulation  and  Notes.  —  Set  up  the  apparatus 
shown  in  Fig.  29,  long  tubes  toward  generator.  Water  is 


70 


LABORATORY  STUDIES  IN   CHEMISTRY. 


placed  in  the  bottle  d,  and  in  a  enough  to  cover  the  end  of 
the  glass  tube,  while  b  contains  a  little  limewater.      The 

joints   are  all  air- 
tight. 

Slide  with  cau- 
tion (give  reason) 
several  pieces  of 
marble  into  the 
side- neck  flask, 
and  pour  upon  it 
about  25  cc.  of  di- 
lute hydrochloric 
acid  (half  water), 
and  at  once  close 
the  flask  with  its 
stopper  (note). 

When  the  mutual  action  of  the  marble  and  the  hydro- 
chloric acid  in  the  generator  is  nearly  ended,  study  the  gas 
as  follows  :  Kemove  the  tube  from  the  bottle,  and  introduce 
a  splinter  flame  (note). 

(a)  Is  this  gas  heavier,  or  lighter,  than  air  ?     When  the 
bottle    has    stood    uncovered    for   a 

little  time,  test  witli  the  flame 
again  (note).  For  further  evidence 
proceed  to  remove  the  stopper  from 
flask  c,  and  to  hold  the  mouth  of 
this  flask  upon  the  lip  of  a  small 
wide-mouthed  bottle,  as  if  to  pour 
the  gas,  as  shown  in  Fig.  30.  After 
a  minute  put  a  little  limewater  into 
the  bottle  ;  cover  it  with  the  hand, 
and  shake  it  (note). 

(b)  Is  this  gas  soluble  in  water?      Put  some  limewater 
into  a  tube,  and,  without  removing  the  stopper,  pour  a  little 


CARBON,  CARBON  DIOXIDE,  CARBONATES.       77 


of  the  water  from  flask  a  into  it,  as  shown  in  Fig.  31.    How 
does  this  result  answer  the  question  ? 

(c)  How  does  the  solution  of  this  gas 
behave  toward  litmus  ?  Put  blue  litmus 
water  into  a  tube,  and.  add  the  solution 
of  gas  from  flask  a  (note),  is  the  solu- 
tion basic,  acid,  or  neutral  ? 

(d).  What  is  the  effect  of  boiling  the 
water  solution  of  this  gas  ?  Pour  a  part 
of  the  water  from  the  bottle  d  into  blue 
litmus  to  decide  whether  it  is  a  solution 
of  this  gas  (note).  Boil  the  remainder 
in  a  beaker  for  a  few  minutes,  and  then 
add  it  to  another  portion  of  blue  litmus 
to  decide  whether  it  is  still  a  solution  of  the  gas  (note). 
Explain  the  difference  in  the  two  results. 

General.  —  The  foregoing  experiments  should  reveal  the 
chief  characteristics  of  carbon  dioxide  (name  them),  and 
should  enable  you  to  distinguish  this  gas  from  all  others. 


Fig.  31. 


EXPERIMENT   72. 
Object.  —  To  test  the  mutual  action  of  acids  and  carbonates. 

Manipulation  and  Notes.  —  Put  some  of  the  given  car- 
bonate into  a  test  tube  or  beaker.  Add  dilute  acid  little  by 
little.  After  the  action  has  gone  on  for  sufficient  time,  test 
the  gas  in  the  open  vessel  with  a  splinter  flame. 

Use  (a)  sodium  carbonate  and  hydrochloric  acid ;  (b) 
sodium  carbonate  and  dilute  sulphuric  acid ;  (c)  potassium 
carbonate  and  acetic  acid  ;  (d)  calcium  carbonate  (marble) 
and  dilute  nitric  acid. 

General.  —  These  experiments  teach  you  how  to  identify 
a  carbonate.  How  would  you  proceed  ? 


78          LABORATORY  STUDIES  IN  CHEMISTRY. 

EXPERIMENT   73. 

Object.  — To  study  the  action  of  carbon  dioxide  on  potassium 

hydroxide. 

Manipulation  and  Notes.  —  To  the  delivery  tube  of  a 
generator  attach  a  glass  tube  through  which  gas  may  be 
carried  into  a  strong  solution  of  potassium  hydroxide  con- 
tained in  a  bottle.  Pass  carbon  dioxide  through  the  solu- 
tion until  no  more  is  absorbed.  Blow  the  gas  out  of  the 
bottle.  Then  add  hydrochloric  acid  (note).  Insert  a  flame 
(note).  What  substance  in  the  solution  do  you  detect  by 
these  results  ? 

EXPERIMENT   74. 

Object.  —  To  ascertain  ivhether  the  white  precipitate  made 
in  limewater  by  carbon  dioxide  is  a  carbonate. 

Manipulation  and  Notes.  —  Pass  carbon  dioxide  through 
strong  limewater.  Filter  the  product  and  test  the  white 
precipitate  with  a  little  acid  (note  and  explain). 

General.  —  These  experiments  (73  and  74)  are  typical. 
Many  other  carbonates  may  be  formed  by  the  action  of 
carbon  dioxide  on  hydroxides. 


COMBUSTION. 


79 


XIV.     COMBUSTION. 


Preliminary.  —  Ordinary  fuels  are  organic  substances 
composed  chiefly  of  carbon  and  hydrogen,  with  smaller  pro- 
portions of  oxygen,  while  some,  such  as  wood  and  paper, 
contain  a  few  other  mineral  substances.  Remember  that 
combustion  is  very  rapid  in  oxygen  alone,  does  not  occur 
in  nitrogen  alone,  and  that  the  atmosphere  consists  chiefly 
of  these  two  gases. 

EXPERIMENT   75. 

Object.  —  To  ascertain  what  substances  are  produced  by  the 
burning  of  a  candle. 

Manipulation  and  Notes.  —  Obviously  these  products 
are  in  the  form  of  vapors  or  gases  (ex- 
plain). 

Bring  a  large,  clean,  and  dry  bottle 
down  over  the  flame  of  a  candle,  and 
hold  it  there  for  a  little  while,  as  shown 
in  Fig.  32. 

When  the  action  ceases  (give  reason), 
quickly  place  the  bottle  upright  on  the 
table,  and  cover  it  (note).  One  product 
is  here  suggested  (note).  Test  the  con- 
tents of  the  bottle  with  a  small  splinter 
flame  (note).  Leave  the  bottle  awhile  uncovered.  Test 
again  with  flame  (note).  Test  with  lime  water  (note).  An- 
other product  is  now  detected. 


Fig.  32. 


80  LABORATORY  STUDIES  IN  CHEMISTRY. 


EXPERIMENT    76. 

Object.  —  To  compare  the  products  of  combustion  of  other 
bodies  with  those  of  a  candle. 

Manipulation  and  Notes.  —  Burn  a  splinter  of  wood, 
a  small  roll  of  paper,  alcohol  (by  moistening  a  bit  of  cotton 
attached  to  a  wire  with  the  liquid),  and  a  small  jet  of  gas 
from  the  Bunsen  lamp,  in  dry  bottles,  and  examine  the  prod- 
ucts in  each  case.  Let  no  solid  products  escape  notice. 

General.  —  The  foregoing  experiments  will  enable  you 
to  explain  the  chemical  changes  in  the  combustion  of  fuels 
(note). 

EXPERIMENT  77. 

Object. —  To  detect  the  curhoii,  hi/  which  the  carbon  dioxide 
of  a  burning  c<nidle  is  produced. 

Manipulation  and  Notes.  —  Hold  a  square  of  clean 
dry  window  glass  a  short  time  across  a  candle  flame  just 
below  the  tip  of  it.  Remove  it  before  it  becomes  so  hot  as 
to  break  (note). 

EXPERIMENT   78. 
Object.  —  To  study  the  flame  of  the  Bunsen  lamp. 

Manipulation  and  Notes.  —  Close  the  holes  in  the  tube 
of  the  burner,  and  describe  the  name.  Press  a  clean,  dry, 
cold  glass  down  upon  it,  flattening  the  tip  (note). 

Open  the  holes  in  the  tube  and  describe  the  flame.  Press 
the  cold  glass  down  upon  it  as  before  (note). 

Which  contains  free  carbon,  —  the  luminous,  or  the  non- 
luminous  flame  ?  In  which  case  is  the  gas  mixed  with  air 
before  it  burns  ?  What  would  seem  to  be  the  source  of  the 
light  in  a  luminous  flame  ?  Why  is  a  good  Bunsen  flame 
smokeless  ? 


COMBUSTION.  81 

EXPERIMENT    79. 

Object.  —  To  examine  the  interior  of  a  luminous  flame. 

Manipulation  and  Notes.  —  (a)  For  this  purpose  the 
flame  of  an  alcohol  lamp  is  better  than  that  of  a  candle, 
because  it  is  larger.  Lay  the  body  of  a  match  across  the 
flame  just  above  the  wick,  and  leave  it  there  only  long 
enough  for  the  flame  to  scorch  it  (note).  Judge  in  what 
part  of  the  flame  the  chemical  action  occurs  (note). 

(b)  Press  a  square  of  paper  down  upon  the  flame  almost 
to  the  tip  of  the  wick,  and  remove  it  as  soon  as  you  see  the 
upper  surface  scorch,  and  before  the  paper  takes  fire  (note). 
In  what  part  of  the  flame  is  the  chemical  action  located  ? 

(c)  Thrust  the  head  of  a  match  quickly  into  the  interior 
of  the  flame  just  above  the  wick'(note).     Does  combustion 
go  on  in  the  interior  of  a  luminous  flame  ?     You  can  give  a 
reason. 

EXPERIMENT   SO. 

Object.  —  To  study  the  combustion  of  charcoal  in  contact 
with  hot  potassium  nitrate. 

Manipulation  and  Notes.  —  Put  about  3  g.  of  potas- 
sium nitrate  into  a  porcelain  crucible,  whose  capacity  is 
about  20  cc.,  and  heat  it  by  a  Bunsen  flame.  You  will 
learn  whether  it  can  be  melted  without  decomposition 
(note).  You  will  learn  also  whether  it  can  be  boiled  with- 
out chemical  change  (note).  When  it  boils,  drop  upon  its 
surface  a  small  splinter  of  charcoal  (note). 

Consider  whether  the  burning  charcoal  gets  its  oxygen 
from  the  air  in  the  crucible  or  from  the  nitrate,  judging  by 
the  way  it  burned.  Or  you  may  try  burning  it  in  a  cruci- 
ble that  contains  no  nitrate.  Is  the  potassium  nitrate  an 
oxidizing  agent  ?  Explain. 
6 


PAUT   II. 


REACTIONS    AND    PROPERTIES    OF    SOME 
COMPOUNDS    OF   METALS. 


I.     POTASSIUM   (K),  SODIUM  (Na),  AMMONIUM 
(NH4). 


EXPERIMENT   81. 

Object.  —  To  study   the  mutual  action   of  potassium    and 
water.    . 

Manipulation  and  Notes.  —  Put  about  100  cc.  of  water 
into  a  bottle.  Drop  into  it  a  piece  of  potassium  not  larger 
than  a  small  pea  (CAUTION  J),  and  cover  it  with  a  glass  plate 
(note).  Does  the  water  show  any  evidence  that  a  new  sub- 
stance is  contained  in  it  ?  Touch  the  tongue  with  a  glass 
rod  moistened  with  it.  What  does  its  taste  suggest  ? 

What  is  its  action  on  litmus  '/  I 're pare  two  tubes,  —  one 
containing  blue  litmus,  the  other  red  litmus,  —  and  pour 
some  of  the  liquid  into  each  (note).  Is  the  product  an  acid, 
an  hydroxide,  or  a  neutral  substance  ?  Name  it.  Write  and 
explain  the  reaction  of  the  metal  and  water. 

What  would  ba  produced  by  the  action  of  carbon  dioxide 
on  the  liquid  in  the  bottle? 

i  Use  a  small  piece,  and  stand  at  a  little  distance  while  the  action 
goes  on. 

82 


POTASSIUM,    SODIUM,    AMMONIUM.  83 

EXPERIMENT   82. 

Object.  —  To  obtain  potassium  carbonate  from  ashes. 

Manipulation  and  Notes.  —  Pack  a  filter  of  usual  size 
about  two  thirds  full  of  wood  ashes.  Pour  hot  water  upon 
them  to  nearly  h'll  the  filter.  Let  it  pass  through.  Pour 
the  nitrate  back  upon  the  ashes.  In  this  way  repeat  the 
filtration  three  or  four  times.  Mention  any  qualities  of  the 
filtrate  which  you  can  detect.  Test  a 'small  part  of  it  with 
acid  (note). 

Finally  evaporate  the  filtrate  carefully  to  dryness  (note). 
Prove  that  the  residue  contains  a  carbonate. 

General.  —  This  experiment  illustrates  the  leaching  pro- 
cess by  which  crude  potassium  carbonate  is  made  on  a  large 
scale  from  wood  ashes  for  use  in  arts  and  industries. 
From  potassium  carbonate  many  other  salts  of  potassium 
are  made. 

EXPERIMENT  83.1 

Object.  —  To  prepare  potassium    chloride  from  potassium 
carbonate. 

Manipulation  and  Notes.  —  Dissolve  about  5  g.  of 
K2C03  in  50  cc.  of  water.  Then  add  HC1  slowly,  until, 
after  shaking  it,  the  liquid  will  redden  a  bit  of  blue  litmus 
paper.  Finally  evaporate  the  liquid  to  a  small  bulk  and 
let  it  cool.  Pour  the  liquid  away  from  the  crystals,  and 
dry  them  on  filter  paper. 

Why  was  the  litmus  paper  used?  What  reaction  took 
place  ?  Prove  that  the  product  is  a  chloride.  Keep  this 
potassium  cMorUe  (KC1). 

1  Two  or  more  of  the  following  experiments  may  go  on  at  once, 
and  much  time  be  thus  saved  which  would  otherwise  be  spent  in 
waiting. 


84          LABORATORY  STUDIES  IN  CHEMISTRY. 


EXPERIMENT   84. 

Object.  —  To  prepare  potassium  nitrate  from  potassium  car- 
bonate. 

Manipulation  and  Notes.  —  Proceed  as  directed  in  the 
preceding  experiment,  using  nitric  instead  of  hydrochloric 
acid.  If  the  evaporation  is  carried  far  enough,  you  can 
watch  the  crystals  growing  in  the  liquid  while  it  cools. 

Write  and  explain  the  reaction.  Prove  that  the  product 
is  a  nitrate.  Keep  this  potassium  nitrate  (KN03). 

EXPERIMENT    85. 

Object.  —  To  study  tlie  mutual  action  of  sodium  and  water. 

Manipulation  and  Notes.  — Put  KM)  cc.  of  water  into 
a  wide-mouthed  bottle.  Drop  in  upon  it  a  piece  of  sodium 
as  large  as  a  small  pea.  Cover  the  bottle  with  a  glass 
plate  (note). 

Test  the  gas  in  the  bottle  with  a  splinter  Maine  (note). 
Point  out  any  apparent  difference  between  this  action  of 
sodium  and  that  of  potassium  on  water. 

Test  for  the  taste  of  the  liquid  (note).  Test  the  action  of 
the  liquid  with  litmus,  and  decide  whether  the  product  of  the 
action  is  an  acid,  an  hydroxide,  or  a  neutral  substance. 

EXPERIMENT  86. 

Object.  —  To    convert  sodium   carbonate   into  other  salts  of 
sodium. 

Manipulation  and  Notes.  —  Follow  the  directions  given 
in  Exps.  83  and  84  for  the  preparation  of  salts  of  potassium. 
In  each  case  write  and  explain  the  reaction,  and  name  the 
salt  produced. 

Use  («-)  hydrochloric  acid,  (b)  nitric  acid,  (c)  sulphuric  acid. 


POTASSIUM,    SODIUM,   AMMONIUM.  85 

EXPERIMENT   87. 

Object.  —  To  convert  ammonium  carbonate  into  other  ammo- 
nium salts. 

Manipulation  and  Notes.  —  Proceed  as  directed  in  the 
preparation  of  potassium  salts.  Use  (a)  hydrochloric  acid, 
(/>)  nitric  acid. 

General.  —  The  foregoing  experiments  show  a  very  marked 
chemical  resemblance  between  potassium  and  sodium  (ex- 
plain), and  between  the  salts  of  potassium,  sodium,  and 
ammonium  (explain ) . 

EXPERIMENT   88. 
Object.  —  To  study  the  action  of  heat  on  salts  of  potassium, 

sodium,  and  ammonium. 

Manipulation  and  Notes.  —  Place  a  very  small  quan- 
tity of  the  given  salt  in  a  porcelain  dish,  and  heat  it  gradu- 
ally.   Describe  the  change,  and  finally  point  out  any  marked 
difference  between  the  three  classes  of  salts. 
Use  (a)  the  carbonates,  (U)  the  chlorides. 

EXPERIMENT   89. 

Object.  —  To  study  the   action    of  potassium,  sodium,  and 
ammonium  salts  on  flame. 

Manipulation  and  Notes. —  Bend 
one  end  of  a  piece  of  platinum  wire 
into  a  round  loop  about  as  large  as  this 
O-  Moisten  this  loop,  and  plunge  it 
into  the  salt  to  be  tested.  A  little  of 
the  salt  will  cling  to  the  wire.  Hold 
it  in  the  mantle  of  a  colorless  flame, 
as  in  Fig.  33  (note). 

Look  at  this  colored  flame  through  a  piece  of  cobalt-blue 
glass  (note). 


86  LABORATORY   STUDIES   IN   CHEMISTRY. 

After  each  trial,  thoroughly  wash  and  heat  the  loop  before 
using  it  with  another  salt. 

(a)  For  potassium  salts  use  the  chloride,  the  nitrate,  and 
the  carbonate  (note}. 

The  color  will  sometimes  come  more  surely  if  the  loop 
is  moistened  with  hydrochloric  acid.  Try  potassium  car- 
b .mate  without  hydrochloric  acid,  and  then  with  it  (note). 

(b)  For    sodium    salts    use   the    chloride  moistened,  the 
nitrate,  and   the   carbonate  without  and  with  hydrochloric 
acid  (note). 

(c)  For  ammonium  salts  use  the  chloride,  the  nitrate,  or 
sulphate,  or  carbonate  (note). 

(d)  Make  a  mixture  of  a  sodium  and  a  potassium  salt, 
and  burn  the  mixture  on  the  platinum  loop.     Which  color 
can  you    get  with    the   naked   eye  ?     Which    if   you    look 
through  cobalt  glass  ? 

General.  —  The  two  preceding  experiments  reveal  some 
well-marked  differences  in  the  actions  of  potassium,  sodium, 
and  ammonium  salts,  by  which  one  should  be  able  to  decide 
whether  a  given  salt  belongs  to  one  or  another  of  these 
classes. 

For  the  potassium  hydroxide  test  for  ammonium  salts, 
see  Exp.  58. 

Non- volatile  compounds  cannot  color  flames  ((/ire  reason). 

For  practice,  prove  the  salts  prepared  in  Exp.  84  to  be 
potassium  salts,  those  in  Exp.  8(5  to  be  sodium  salts,  those 
in  Exp.  87  to  be  ammonium  salts.  Try  other  specimens 
also. 


CALCIUM,    BARIUM,    STRONTIUM.  87 


II.     CALCIUM  (Ca),  BARIUM  (Ba),  STRONTIUM  (Sr). 


EXPERIMENT   9O. 

Object.  —  To  convert  calcium  carbonate  into  calcium  chloride. 
Manipulation  and  Notes.  —  Reduce  a  small  piece  of 
marble  to  coarse  powder,  and  add  it  little  by  little  to  5  cc. 
of  hydrochloric  acid  in  a  test  tube  (note}.  What  is  the 
escaping  gas  ?  Can  any  solid  product  be  seen  in  the  liquid  ? 
Write  the  reaction  which  should  be  expected  between  the 
two  substances  used,  and  judge  thereby  what  product  should 
be  in  the  liquid.  Evaporate  the  liquid.  Do  you  find  the 
suspected  substance  ?  Why,  then,  did  it  not  appear  in 
the  liquid  ?  To  answer  this  last  question,  try  the  solubility 
of  the  product  in  water. 

EXPERIMENT   91. 

Object.  —  To  convert  calcium  chloride  into  calcium  carbonate. 

Manipulation  and  Notes.  —  Place  about  5  cc.  of  cal- 
cium chloride  in  a  test  tube,  add  about  as  much  water,  and 
heat  the  mixture  to  boiling  point  (give  reason).  Then  add 
slowly  a  solution  of  ammonium  carbonate  as  long  as  it 
continues  to  produce  the  precipitate.  To  know  when  to 
stop,  let  the  solid  settle  a  little,  and  then  notice  whether 
another  drop  of  the  ammonium  carbonate  has  any  effect 
(note).  The  white  precipitate  is  calcium  carbonate.  Why 
does  it  appear  as  a  precipitate  ?  To  answer  this  question, 
try  the  solubility  of  calcium  carbonate  in  water. 

Write  the  reaction,  and  decide  what  else  was  probably 
produced.  Why  was  not  this  substance  also  precipitated  ? 


LABORATORY  STUDIES  IN   CHEMISTRY. 

Is  there  any  calcium  compound  left  in  the  liquid  ?  This 
should  teach  you  how  to  get  all  the  calcium  out  of  any  liquid 
which  contains  its  salts  in  solution.  You  can  also  give  the 
reason  why  no  precipitates  were  obtained  in  the  experiments 
with  potassium,  sodium,  and  ammonium  salts. 

EXPERIMENT    92. 

Object. —  To  compare  the  reactions  of  calcium,  barium,  and 

strontium  salts. 

Manipulation  and  Notes.  —  (a)  Arrange  three  tubes, 
each  with  5  cc.  of  water,  and  add  to  one  5  cc.  of  a  solution 
of  calcium  chloride  (CaCL);  to  the  second,  5  cc.  of  solu- 
tion of  barium  chloride  (HaCU);  to  the  third,  5  cc.  of 
solution  of  strontium  chloride  (SrCl2).  Then  add  to  each, 
drops  of  ammonium  carbonate,  (NH4)2(.-<)3  (note).  Point 
out  the  resemblances  of  these  products  to  one  another. 
Write  the  reactions,  and  note  their  great  similarity. 

(b)  Use  solutions  of    the  nitrates  of   these   metals,  and 
proceed  as  in  (a). 

(c)  Use  the  chlorides  ;  add  NH4  Cl  to  the  solutions  ;  then 
add  the  (NH4)2CO3.     Does  the  presence  of  NH4(U  hinder 
the  production  of  the  precipitate  ? 

(d)  Try  to  dissolve  a  little  of  the  precipitate  in  NH4  OH 
(note). 

General.  —  All  the  corresponding  compounds  of  these 
three  metals  exhibit  very  close  resemblances,  and  their  re- 
actions throughout  are  similar. 

EXPERIMENT    93. 

Object.  —  To  study  some  differences  in  the  reactions  of  ba- 
rium, calcium,  and  strontium  salts. 

Manipulation  and  Notes.  —  (a)  The  reaction  with 
CaS04.  Arrange  three  test  tubes,  each  with  5  cc.  of 


CALCIUM,    BARIUM,    STRONTIUM.  89 

water,  and  add  to  one  5  cc.  of  strong  solution  of  BaCl2, 
to  the  second  as  much  strong  solution  of  SrCl2,  and  to 
the  third  as  much  strong  solution  of  Ca  C12 .  Then  add  to 
each  a  little  solution  of  calcium  sulphate  (CaS04).  Note 
whether  precipitates  are  formed  at  once  in  the  cold  solu- 
tions. Heat,  to  boiling,  those  in  which  no  precipitate  has 
appeared  (note).  Point  out  the  difference  in  the  behavior 
of  the  Ba,  Sr,  and  Ca  salts  in  this  reaction. 

(b)  The  flame  coloration.  Follow  directions  given  for 
the  flame  test  in  Exp.  89.  Use  the  chlorides  (note).  Use 
the  carbonates  (note).  Use  the  carbonates  moistened  with 
HC1  (note).  Observe  the  flames  through  cobalt  glass  (note). 
Point  out  the  difference  between  these  and  the  flame  colors 
of  potassium  and  sodium. 

General.  —  By  the  peculiarities  revealed  in  the  foregoing 
experiment  you  should  be  able  to  distinguish  the  Ba,  Sr, 
and  Ca  compounds  from  one  another,  and  also  from  those 
of  K,  Na,  andNH4. 

For  practice,  examine  substances  which  may  be  given  by 
the  instructor,  and  try  to  decide  whether  each  one  is  a  com- 
pound of  Ca,  Sr,  or  Ba. 


90          LABORATORY  STUDIES  IN   CHEMISTRY. 


III.     MAGNESIUM  (Mg). 


EXPERIMENT    94. 

Object.  —  To  study  the  reactions  of  soluble  magnesium  com- 
pounds with  ammonium  carbonate. 

Manipulation  and  Notes.  —  (a)  Arrange  two  tubes,  each 
with  about  5  cc.  of  water.  Add  to  one  tube  about  5  cc.,and 
to  the  other  about  ^  cc.,  of  magnesium  chloride  (Mg012). 
Heat  the  strong  solution,  and  add  ammonium  carbonate 
(NH4).2C03  (note).  Treat  the  weak  solution  in  the  same 
way  (note). 

The  product  obtained  from  the  strong  solution  is  mag- 
nesium carbonate  (MgCO3),  which  is  insoluble  in  water;  but 
in  weak  solution  the  product  is  double  carbonate  of  magne- 
sium and  ammonium  (MgCO3  (NH4)2C03),  which  is  soluble. 

(b)  Is  MgC03  soluble  in  NH4C1  ?  To  answer  this  ques- 
tion, transfer  a  little  of  the  carbonate  obtained  from  strong 
solution  to  another  tube,  and  add  considerable  NH4C1. 

(V)  Can  the  precipitate  be  obtained  in  presence  of  much 
NH4C1?  Mix  5  co.  of  NH4C1  with  5  cc.  of  Mg012,  and 
then  add  the  (NH4).2  CO3 .  Why  is  no  precipitate  formed? 

Write  the  reaction  which  occurred  in  (a).  You  can  judge 
from  this  reaction,  in  the  light  of  (b)  and  (V),  whether  you 
should  ever  expect  to  precipitate  all  the  magnesium  in  a 
solution  by  means  of  ammonium  carbonate  (note). 

(cl)  Is  MgCO3  soluble  in  NH4OH  ?  Try  a  little  of  the 
precipitate  with  NH4OH,  as  you  did  with  NH4C1  in  (b) 
(note).  Would  NH4OH  prevent  the  precipitation  of  the 
carbonate,  as  did  NH4C1?  Would  HC1  prevent  the  pre- 
cipitation of  the  carbonate  ?  WThy  ? 


ZINC.  91 


IV.     ZINC  (Zn). 


EXPERIMENT    95. 

Object.  —  To  study  the  reaction  of  ammonium  carbonate  ivith 
soluble  compounds  of  zinc. 

Manipulation  and  Notes.  —  Use  zinc  chloride  (ZnCl2). 
Add  a  few  drops  of  solution  of  Zn  C12  to  10  cc.  of  water, 
and  then  add  (NH4)2C03  (note). 

Write  the  reaction,  and  name  the  zinc  product. 

Ascertain  whether  NH4C1  will  prevent  the  foregoing 
result,  as  it  does  the  similar  reaction  with  MgCl2. 

EXPERIMENT   96. 

Object.  —  To  study  the  reaction  of  ammonium  hydroxide 
with  zinc  chloride. 

Manipulation  and  Notes To  a  few  cubic  centime- 
ters of  the  ZnClo  mixed  with  an  equal  bulk  of  water,  add 
NH4OH  little  by  little  (note).  Continue  to  add  the  hy- 
droxide, until  after  shaking  it,  and  then  blowing  the  air  out 
of  the  tube,  the  strong  odor  of  ammonia  remains  (note). 

Write  the  reaction  and  name  the  zinc  product.  This 
compound  of  zinc  is  insoluble  in  water,  but  it  is  soluble  in 
ammonium  hydroxide.  Does  this  explain  the  results  just 
now  obtained  ? 

When  a  precipitate  is  dissolved  by  the  reagent  which 
produces  it,  it  is  said  to  be  soluble  in  excess. 


92  LABORATORY  STUDIES  IN   CHEMISTRY. 

EXPERIMENT   97. 

Object.  —  To  study  the  reaction  of  zinc  chloride  with  hydro- 
gen sulphide. 

Manipulation  and  Notes.  —  (a)  Put  about  4  cc.  of 
strong  solution  of  JhLS  into  a  tube,  and  add  a  solution 
of  ZnCLj  drop  by  drop  (note). 

(b)  Itepeat  the  experiment,  varying  it  by  adding  a  drop 
of  HOI  to  the   chloride,  so  that  the  ZnCL,  is  in  an  acid 
solution  (note). 

(c)  Repeat   the  experiment,  varying    it   by  making   the 
zinc  chloride  alkaline    by  adding  drops  of   NH4OH  until 
the  hydroxide  formed  at  first  is  dissolved  in  excess  (note). 

Write  the  reaction  of  ZnCL  with  H2S. 
What  is  the  action  of  the  H  Cl  in  (b)  \> 
What  is  the  action  of  the  NH4()H  in  (v)  ? 

(d)  To  10  cc.  of  water  add  drops  of  ZnCl2,  and  then  a 
drop  or  two  of  ammonium  sulphide   (NH4HS).     Compare 
the  product  with  the  sulphide  obtained  in  (c).     Write  the 
reaction. 

General. — The  foregoing  experiment  has  shown  what 
reagents  may  be  used  to  convert  any  soluble  compound  of 
zinc  into  zinc  sulphide  (explain}  ;  the  condition  necessary 
in  order  to  obtain  the  sulphide  as  a  precipitate  (explain)  ; 
its  color,  and  something  about  its  solubility  in  water,  in 
acids,  and  in  hydroxides. 

Suggestion.  —  Instead  of  using  H2  8  in  solution  to  pro- 
duce the  sulphide  of  metals,  the  gas  itself  will  be  found 
much  more  active,  and  much  more  satisfactory  in  every 
respect  but  one ;  and  that  is,  the  difficulty  in  using  the  gas 
without  suffering  from  its  odor.  A  generator  large  enough 
to  supply  the  gas  for  all,  and  fixed  in  a  good  ventilating 
chamber,  may  be  used.  Or,  if  a  student  can  be  trusted  to 


z/jvc.          ' 

be  steadfastly  careful,  he  may  use -a  small  gas  apparatus 
consisting  of  a  side-neck  tube  generator,~~ana  tKree  small 
wide-mouthed  bottles,  a,  b,  c,  in  place  of  the  usual  conical 
flasks,  with  long  tubes  toward  generator.  The  bottle  a  may 
be  moderately  packed  with  cotton  wool,  or  contain  a  little 
water,  to  intercept  substances  carried  over  by  the  gas.  In 
b  the  solution  to  be  treated  should  be  placed,  and  c  should 
contain  dilute  ammonium  hydroxide  (half  water)  to  absorb 
the  excess  of  gas  which  would  otherwise  poison  the  atmos- 
phere. 

For  each  experiment,  ferrous  sulphide  (only  enough  for 
the  experiment)  should  be  put  into  the  generator.  Acid, 
made  so  dilute  that  a  steady  but  slow  stream  of  gas  is 
evolved,  should  be  added.  All  joints  should  be  tight ;  and 
the  generator  should  exhaust  itself  before  b  is  removed. 
Remove  b  by  slipping  it  from  the  stopper,  and  then  let  the 
apparatus  stand  ready  for  the  next  call  upon  it.  The  am- 
monia in  c  will  need  changing  only  when  it  has  become 
yellow. 


94  LABORATORY  STUDIES  IN  CHEMISTRY. 


V.     CADMIUM    (Cd). 


EXPERIMENT   98. 

Object.  —  To  study  the  reaction  of  cadmium   chloride  with 

ammonium  carbonate, 

Manipulation  and  Notes.  —  Use  a  solution  of  cadmium 
chloride  (CdCl2),  and  follow  the  directions  given  in  Exp.  94 
(note). 

EXPERIMENT    99. 

Object.  —  To  study  the  reaction  of  cadmium  chloride  with 

ammonium  hydroxide. 

Manipulation  and  Notes.  —  Follow  the  directions  given 
in  Exp.  96  (note). 

EXPERIMENT   1OO. 
Object.  —  To  study  the  reaction  of  cadmium  chloride  with 

hydrogen  sulphide. 

Manipulation  and  Notes.  —  Adopt  the  plan  given  in 
detail  in  Exp.  97,  (a),  (b),  (c),  (d),  discussing  all  the  results 
as  fully  as  you  can. 

Compare  the  sulphides  of  cadmium  and  zinc. 

A.     EXERCISE  IN  COLLECTING  AND  TABULATING 

RESULTS  OF  EXPERIMENTS. 

Object. —  To  compare  the  carbonates  of  barium,  strontium, 
calcium,  mag?iesium,  zinc,  potassium,  sodium,  and  am- 
monium. 

Prepare  a  skeleton  table  like  that  on  p.  95.  In  the  first 
column  put  the  symbols  of  the  metals  whose  carbonates  are 


CADMIUM. 


95 


to  be  compared.  In  the  second  column  put  the  formulas  of 
the  carbonates.  Head  the  following  columns  with  the  par- 
ticular facts  in  regard  to  which  you  wish  to  compare  them. 
Consult  your  notes  of  the  experiments  you  made  with  each, 
and  state  the  fact  for  each  in  its  proper  blank.  If,  in  any 
case,  your  experiments  have  not  revealed  the  fact  directly, 
nor  enabled  you  to  -infer  it  with  certainty,  leave  the  blank 
unfilled.  If  your  experiment  has  revealed  no  change,  show 
this  by  a  dash  drawn  in  the  blank. 

Table :  Comparison  of  Properties  of  some  Carbonates. 


METALS. 

CARBON- 
ATES. 

COLOK. 

SOL'Y  IN 
H2O 

SOL'Y  IN 
H  Cl 

SOL'Y  IN 
NH4  Cl 

SOL'Y  IN 
NH4  OH 

Ba 

Sr 

BaCO3 

White. 

Insol. 

Soluble  to 
BaCla 

Insol. 

Insol. 

Ca 

Mg 

Zn 

K 

Na 

NH4 

By  what  reagent  may  the  soluble  compounds  of  Ca  be 
converted  into  CaC03  ?  (Exp.  91.) 

In  what  respect  do  the  carbonates  of  K,  Na,  and  NH4 
differ  from  all  the  others,  and  resemble  one  another  ?  What 
does  the  table  show  in  regard  to  the  carbonates  of  Ba,  Sr, 
Ca  ?  In  what  respects  is  MgC03  related  to  those  of  Ba,  Sr, 
Ca  ?  Wherein  does  it  differ  ? 

If  a  solution  contains  the  six  metals,  Ba,  Sr,  Ca,  K,  Na, 
and  NH4 ,  in  the  form  of  chlorides,  by  what  reagent  could 
you  precipitate  three  of  them  in  the  form  of  carbonates, 
and  leave  the  other  three  in  solution  ? 


96  LABORATORY  STUDIES  IN   CHEMISTRY. 


VI.     MERCUEY    (Hg). 


EXPERIMENT  1O1. 

Object.  —  To   study    the   reaction   of  mercury   with   nitric 

acid. 

Manipulation  and  Notes.  —  (a)  Into  one  tube,  a,  put 
a  small  globule  of  mercury  ;  into  another  tube,  /;,  put  a 
small  globule  of  the  same  metal.  To  the  metal  in  tube  a 
add  1  cc.  of  dilute  nitric  acid  (note),  and  let  stand  in  the 
rack  until  action  ceases.  To  the  metal  in  tube  b  add  1  cc. 
of  moderately  strong  nitric  acid,  and  apply  heat  (note). 
What  salt  of  mercury  is  probably  produced  in  the  tubes  ? 

(b)  To  5  cc.  of  water  add  drops  of  the  clear  liquid  in 
tube  a.j  and  then  add  drops  of  HC1  (note).    To  5  cc.  of  water 
add  drops  of  clear  liquid  from  tube  b,  and  then  drops  of 
HC1  (note).     If  you  get  the  same  results,  you  are  entitled 
to  say  that  the  same  salt  is  made  by  the  nitric  acid  in  both 
tubes  :  is  it  so  ? 

(c)  Take  the  clear  liquid  from  a.  and  heat  it  to  boiling. 
Add  a  drop  or  two  of  concentrated  nitric  acid,  and  boil 
again.     Put  drops  of  this  liquid  into  5  cc.  of  water,  and  add 
HC1  (note).     Compare    with   results  in   b.     You   can    now 
judge  whether  this  liquid  contains  the  same  salt  it  contained 
before  boiling  with  HN03. 

General.  —  This  study  should  reveal  the  fact  that  mer- 
cury is  capable  of  yielding  two  salts  with  nitric  acid.  We 
have  mercurous  nitrate  (Hg2(N03)2)  in  tube  a,  and  mer- 
curic nitrate  (Hg  (K08)2)  in  tube  b. 

This  twofold  action  of  mercury  is  general.  There  are 
two  classes  of  mercury  compounds. 


MERCURY.  97 

(d  )  Is  mercurous  chloride  soluble  in  water  ?  To  10  cc.  of 
water  add  a  few  drops  of  mercurous  nitrate,  and  then  H  Cl 
drop  by  drop,  carefully,  until  a  drop  produces  no  change. 
Do  not  add  excess.  The  tube  now  contains  the  chloride 
mixed  with  water.  Transfer  a  little  to  another  tube,  add 
more  water,  and  shake  vigorously.  In  this  way  you  can 
j  udge  whether  it  is  soluble  in  cold  water.  Heat  the  mixture 
and  judge  whether  it  is  soluble  in  hot  water. 

(e)  Is  mercurous  chloride  affected  by  NH4  OH  ?  Treat 
the  chloride  remaining  from  (d)  with  drops  of  NH4OH 
(note). 

EXPERIMENT   1O2. 

Object.  —  To  study  the  effect  of  ammonium  hydroxide  on 
soluble  mercurous  and  mercuric  compounds. 

Manipulation  and  Notes.  —  Add  a  few  drops  of  strong 
solution  of  the  given  compound  to  5  cc.  of  water,  and  then 
add  the  NH4OH  drop  by  drop  to  excess  (Exp.  96). 

Use  (a)  solution  of  mercurous  nitrate  (note),  (b)  solution 
of  mercuric  chloride  (note). 

General.  —  The  actions  of  H  Cl  011  mercurous  and  mer- 
curic compounds,  generally,  are  the  same  as  upon  the  two 
nitrates  in  (b*),  Exp.  101.  The  actions  of  NH4  OH  on  mer- 
curous nitrate  and  mercuric  chloride  are  also  typical  of  its 
action  on  the  ous  and  the  ic  compounds  generally.  You 
can  use  these  reactions  to  decide  whether  a  given  sub- 
stance is  a  mercurous  or  a  mercuric  compound  (explain). 

EXPERIMENT   1O3. 

Object.  —  To  study  the  reaction  of  compounds  of  mercury 

with  hydrogen  sulphide. 

Manipulation  and  Notes.  —  (a)  Use  mercurous  nitrate, 
and  proceed  as  directed  in  («),  Exp.  97  (vote). 
7 


98  LABORATORY  STUDIES  IN   CHEMISTRY. 

(b)  Use  mercuric  chloride,  and  proceed  in  the  same  way 
(note).     What  differences,  if  any,  can  you  discover  in  the 
two  experiments  ?     What  differences  in  the  two  sulphides 
produced  ? 

(c)  Use  mercuric  chloride  in  acid  solution. 

(d)  Use   mercuric   chloride    in   alkaline    solution.      Add 
drops  of  NH4OH  (note),  then  treat  it  with  the  H2S  (note, 
explain). 

(e)  Use  dilute  solution  of  HgCl2,  and  treat  it  with  am- 
monium sulphide,  as  in  Exp.  97  (d). 

(/)  Is  this  sulphide  soluble  in  HN03  ?  To  answer  this 
question,  proceed  as  follows :  First  obtain  the  clean  sul- 
phide. For  this  purpose  filter  it  out  of  the  liquid,  and 
then  wash  it  by  pouring  water  into  the  filter,  enough  to 
cover  the  sulphide,  letting  it  run  through,  and  repeating 
the  operation.  Remove  the  filter  from  the  funnel,  open  it 
out,  and  lay  the  paper  flat  upon  a  glass  plate.  Then  with 
a  spatula  transfer  a  very  little  of  the  sulphide  from  the 
paper  to  a  porcelain  dish  ;  cover  it  with  dilute  HN03 ,  and 
stir  it  with  a  glass  rod.  If  it  do  not  dissolve  in  the  cold, 
apply  a  gentle  heat.  If  it  do  not  dissolve  in  the  hot  dilute 
acid,  try  concentrated  acid  in  the  same  way. 

EXPERIMENT   1O4. 

Object.  —  To    liberate    metallic    mercury  from    mercurous 

chloride. 

Manipulation  and  Notes.  —  Use  a  bright  piece  of 
copper  wire.  Acidify  a  dilute  solution  of  the  chloride  with 
a  drop  of  HC1,  and  insert  a  piece  of  bright  copper  wire. 
After  a  little  time  observe  the  coating  on  the  wire.  Its 
appearance,  especially  after  being  rubbed  with  a  cloth,  will 
be  likely  to  inform  you  what  this  coating  is.  Mercury  is 
volatile  :  test  this  coating  by  heating  the  wire  (note). 


SILVER.  99 


VII.     SILVER   (Ag). 


EXPERIMENT   1O5. 

Object.  —  To  study  the,  reaction  of  silver  nitrate  with  Injdro- 
chloric  acid. 

Manipulation   and  Notes (a)    To  10   cc.   of   water 

add  4  or  5  drops  of  AgNOg,  and  then  drops  of  HC1  (note). 
Shake  it  vigorously  (note).     Write  the  reaction. 

(b)  Is  silver  chloride  soluble  in  hot  water  ?     Put  a  little 
of  that  just  made  into  a  little  water  in  another  tube,  and 
heat  to  boiling. 

(c)  Is   this   chloride   affected  by  NH4OH?     Transfer  a 
little  to  another  tube,  and  add  drops  of  NH4  OH. 

(d)  How  is  it  affected  by  light  ?     Recall  the   result  of 
a  former  experiment,  or  expose  the  remainder^  of  the  chlo- 
ride made  in  (a)  to  direct  sunlight. 

EXPERIMENT   1O6. 

Object.  —  To  convert  silver  nitrate  into  silver  sulphide. 

Manipulation  and  Notes.  —  (a)  Pass  H2  S  through  a 
dilute  solution  of  AgN03,  or  add  drops  of  the  AgN03  solu- 
tion to  5  cc.  of  the  solution  of  H2S  in  water  (note).  Write 
the  reaction. 

(/>)  To  a  dilute  solution  of  AgN03  add  drops  of  ammo- 
nium sulphide  in  slight  excess.  An  excess  will  be  present 
when  the  liquid  retains  the  odor  of  this  reagent,  or  if, 
when  the  precipitate  settles  sufficiently,  you  can  detect  the 
color  of  the  reagent  in  the  liquid  (note).  Write  the  reac- 
tion. What  evidence  that  the  same  sulphide  is  obtained  in 
(a)  and  (b)  ? 


100        LABORATORY   STUDIES   IN    CHEMISTRY. 

EXPERIMENT   1O7. 
Object.  —  To  liberate  metallic  silver  from  silver  nitrate. 

Manipulation  and  Notes.  —  (a)  Use  a  bright  piece  of 
copper,  as  inExp.  104,  omitting  the  HC1  (yive  reason).  ( )b- 
serve  the  coating  which  gathers  on  the  wire :  it  is  metallic 
silver. 

(b)  Use  a  globule  of  mercury.  Put  the  globule  into  a 
little  dish,  and  cover  it  with  concentrated  solution  of 
AgN03?  and  let  it  stand. 


COPPER.  101 


VIII.     COPPER  (Cu). 


EXPERIMENT   1O8. 

Object.  —  To  ascertain  the  action  of  hydrochloric  acid  with 
soluble  compounds  of  copper. 

Manipulation  and  Notes.  —  Use  dilute  solution  of  cop- 
per sulphate  (CuSO4).  Add  1  cc.  of  the  copper-sulphate 
solution  to  10  f.e.  of  water,  and  half  as  much  hydrochloric 
acid,  drop  by  drop  (note). 

Has  the  sulphate  been  converted  into  the  chloride?  To 
answer  this  question,  evaporate  the  liquid  to  crystallization, 
and,  after  rinsing  the  crystals  in  water  to  rid  them  of  any 
trace  of  II  Cl,  dissolve  in  water;  then  decide  whether  the 
substance  is  a  chloride  by  means  of  AgN03,  followed  by 
NII4OH  (Exp.  38  (a)  (c)  ),  or  a  sulphate  by  means  of  BaCl2 
(Exp.  48). 

What  property  of  Cu012  makes  it  impossible  to  obtain 
it  fts  a  precipitate  from  any  solution  by  means  of  HC1  ? 

EXPERIMENT    1O9. 

Object.  —  To  study  the  preparation  and  properties  of  copper 
sulphide. 

1.     To  OBTAIN  THE  SULPHIDE. 

Manipulation  and  Notes.  —  (a)  Add  about  1  cc.  of 
dilute  solution  of  copper  sulphate  (CuS04)  to  10  cc.  of 
H2  S  solution ;  or,  better,  pass  the  hydrogen-sulphide  gas 
through  the  mixture  until  it  is  saturated  (note).1 

1  If  the  gas  is  used  in  (it),  the  work  in  (/>),  (<•),  and  ((7)  can  go  on 
with  the  H.,S  solution  while  the  gas  is  saturating  the  liquid.  In 
this  way  time  may  be  saved. 


102        LABORATORY  STUDIES  IN   CHEMISTRY. 

(b)  Acidulate  a  solution  of  CuS04  with  HC1,  and  treat 
it  with  the  H2  S  solution  or  gas  (note). 

(c)  Add  a  drop  or  two  of  NH4  OH  to  a  solution  of  Cu  S04 , 
and  then  treat  the  mixture  with  H2S  (note). 

By  these  trials  you  learn  whether  the  sulphide  is  precipi- 
tated equally  well  in  neutral,  acid,  or  alkaline  solution. 
Notice  that  NH4  OH  +  H2S  =  H20  +  NH4HS. 

(d)  To  10  cc.  of  water  add  1  cc.  of  Cu  S04 ,  and  then  a  few 
drops  of  ammonium  sulphide  (NH4HS)  (note).    Judge  from 
the  results  in  (b)  and  (c)  whether  the  one  reagent  (ammo- 
nium sulphide)  may  be  used  instead  of  the  two  (XH4OH 
and  H2  S  together)  for  the  same  result. 

Write  and  explain  the  reactions  in  (a)  and  (d). 

2.     To  DISCOVER  SOME  PROPERTIES  OF  COPPER  SULPHIDE. 

Manipulation  and  Notes.  —  (a)  What  is  the  color  of 
this  sulphide  ?  Recall  any  sulphides  previously  seen  which 
resemble  this  one  ;  also  others  which  are  quite  different. 

(b)  Is  this  CuS  soluble  in  HC1  ? 

(c)  Is  this  Cu  S  soluble  in  HN03  ? 

(d)  Is  this  CuS  soluble  in  yellow  ammonium  sulphide  ? : 

EXPERIMENT   11O. 

Object. —  To    learn    tJie   action    of    ammonium   hydroxide 

with  a  soluble  compound  of  copper. 

Manipulation  and  Notes.  —  Mix  1  cc.  of  solution  of 
Cu  SO4  with  10  cc.  of  water,  and  add  NH4  OH  by  drops, 
shaking  the  tube  well  after  each  drop.  Note  the  effect  of 
the  first  drop,  then  of  additional  drops,  and  finally  of  excess. 

1  The  solution  of  ammonium  sulphide,  prepared  by  saturating 
NIT4OH  with  H2S,  gradually  becomes  yellow.  In  this  condition, 
it  contains  more  than  one  ammonium  sulphide;  and  among  them 
is  the  (NH).2  S,  which  is  a  more  powerful  solvent  than  NH4 HS. 


COPPER.  103 

EXPERIMENT   111. 

Object.  —  To  liberate  the  copper  from  a  soluble  compound  of 
this  metal. 

Manipulation  and  Notes.  — Add  1  cc.  of  dilute  solu- 
tion of  the  given  compound  (say,  CuS04)  to  10  cc.  of  water, 
and  insert  a  bright  piece  of  iron,  —  a  wire,  a  knife  blade  or 
a  nail  (note). 

A  drop  of  H  Cl  may  facilitate  the  action. 

Write  and  explain  the  reaction. 

EXPERIMENT  112. 
Object.  —  To  prove  that  a  dime  contains  copper  and  silver. 

Manipulation  and  Notes.  —  Upon  a  dime  in  a  porcelain 
dish  pour  10  cc.  of  nitric  acid,  half  water,  and  warm  it,  if 
necessary,  to  start  the  chemical  action  (note).  When  the 
action  is  over,  pour  2  cc.  of  the  solution  into  10  cc.  of 
water,  and  add  solution  of  sodium  chloride  as  long  as  it 
has  any  effect  (note).  Filter,  and  wash  the  precipitate  three 
times  with  water. 

Then  prove  that  the  nitrate  contains  copper  by  using  iron 
as  in  Exp.  Ill,  and  that  the  precipitate  contains  silver, 
which  you  can  do  by  showing  (Exp.  105  (b)  (c)  )  that  it  is 
silver  chloride. 


104        LAtiOllATOEY  STUDIES  IN  CHEMISTRY. 


IX.     LEAD    (Pb). 


EXPERIMENT   113. 

Object.  —  To  ascertain  the  action  of  hydrochloric  acid  with 
soluble  compounds  of  lead. 

Manipulation  and  Notes.  —  (a)  Use  a  dilute  solution 
of  lead  nitrate  (PbX03),  and  treat  it  as  AgN03  was  treated 
in  Exp.  105  (a)  (note). 

Next  use  a  strong  solution  of  the  PbN03  in  the  same 
way  (note). 

What  is  the  precipitate  ?  Write  and  explain  the  reaction. 
Why,  probably,  did  it  not  appear  in  the  dilute  solution  ? 

(b)  Is    this    chloride    soluble    in  hot    water  ?     Heat  the 
mixture  obtained  in  (ft)  to  boiling  (note).     Let  the  solution 
stand  until  cold.    In  what  form  does  the  chloride  reappear? 

(c)  Is  there  any  chloride  held  in  solution  by  cold  water  ? 
When  the   tube  has  become  quite  cold,   decant    the    clear 
liquid  and  evaporate  it  almost  to  dryness. 

(d)  Learn   the  effect  of   NH4  OH   on  the   precipitate  of 
PbCl2  by  the  process  in  Exp.  105  (c). 

(e)  Learn  the  effect  of  light  on  this  chloride,  Exp.  105  (d). 

EXPERIMENT   114. 

Object.  —  To  study  the  preparation  and  properties  of  lead 
sulphide. 

1.     To  OBTAIN  THE  SULPHIDE. 

Manipulation  and  Notes.  —  (a)  Use  lead  nitrate  or  lead 
acetate,  and  follow  dir  'ctions  for  CuS  in  Exp.  109,  1  (a). 


LEAD.  105 

(5)  Learn  whether  the  same  result  may  be  obtained  in 
an  acid  solution  of  the  lead  compound.  Follow  directions 
given  in  Exp.  109,  1  (b). 

(c)  Learn  whether  the  same  result  may  be  obtained  in  an 
alkaline  solution  of  the  lead  compound.     Follow  directions 
given  in  Exp.  109,  1  (c). 

(d)  Learn  whether  you  can  obtain  the  sulphide  by  the 
use  of  ammonium  sulphide. 

2.    To  DISCOVER  THE  PROPERTIES  OF  LEAD  SULPHIDE. 

Manipulation  and  Notes.  —  (a)  Obtain  the  clean  sul- 
phide for  examination.  Filter  and  wash  the  precipitate  as 
directed  in  Exp.  103  (/). 

(b)  What  is  the  color  of  this  sulphide  ?     Can  you  dis- 
tinguish it  by  its  appearance  from  CuS?     CdS?     HgS? 
ZnS? 

(c)  Is  this  Pb  S  soluble  in  H  01  ? 

(d)  Is  this  sulphide  soluble  in  HN03  ? 

(e)  Is  lead  sulphide  soluble  in  ammonium  sulphide  ? 

EXPERIMENT   115. 

Object.  —  To  learn  the  action  of  ammonium  hydroxide  with 

a  soluble  compound  of  lead. 

Manipulation  and  Notes.  —  Use  a  solution  of  lead 
nitrate  (Pb(N03)2)  or  of  lead  acetate  (Pb(C2H302)2),  and 
follow  directions  found  in  Exp.  110. 

EXPERIMENT    116. 

Object.  —  To  liberate  lead  from  a  soluble  compound  of  the 

metal. 

Manipulation  and  Notes.  —  Use  the  acetate.  Add  a 
drop  of  H  01 ;  insert  a  strip  of  clean  zinc,  and  let  it  stand, 
to  be  observed  at  intervals  until  you  can  describe  the  result. 


106        LABORATORY  STUDIES  IN   CHEMISTRY. 

Write  the  reaction,  and  compare  it  with  those  in  the  libera- 
tion of  Hg,  Ag,  and  Cu. 

Or  make  the  experiment  on  a  larger  scale,  and  obtain  the 
so-called  "lead-tree,"  as  follows  :  — 

Dissolve  8  or  10  g.  of  lead  acetate,  com- 
monly called  "  sugar  of  lead,"  in  about  500  cc. 
of  water,  and,  if  the  solution  is  cloudy,  add  a 
little  acetic  acid  to  clear  it.     Put  this  solu- 
tion into  a  white  glass  bottle,  and  then  hang 
in  it  a  strip  of  clean  sheet  zinc  (Fig.  34),  and 
let  it  stand  undisturbed  until  the  next  day, 
F[    34          when  you  will  be  able  to  describe  the  beau- 
tiful growth  of  crystals  which  has  long  been 
called  the  "lead-tree." 

EXPERIMENT  117. 
Object.  —  To  obtain  lead  iodide. 

Manipulation  and  Notes.  —  Add  drops  of  a  solution 
of  potassium  iodide  (KI)  to  a  moderately  dilute  solution  of 
lead  nitrate  (Pb  (N03)2)  (note).  Write  the  reaction. 

Heat  the  contents  of  the  tube  (note).  If  the  iodide  is 
visible  after  heating  to  boiling,  add  a  little  water  and 
heat  again.  Let  the  solution  cool  spontaneously  (note). 
Explain  the  changes. 

B.     EXERCISE  IN  COLLECTING  AND  TABULATING 
RESULTS  OF  EXPERIMENTS. 

Object.  —  To  compare   the  properties  of  the  chlorides   of 
silver,  mercury.,  copper,  and  lead. 

Prepare  a  skeleton  table  like  that  on  p.  107.  Fill  the 
blanks  by  gleaning  the  facts  from  your  own  notes,  as 
directed  in  Exercise  A,  p.  94. 


LEAD. 


107 


Table :  Comparison  of  Properties  of  some  Chlorides. 


METALS. 

CHLO- 
RIDES. 

<!OLOR. 

soL'y  IN  H2O 

COLD.                HOT. 

SOL'Y  IN 

HC1 

EFFECT 
OF 

N1I4OH 

EFFECT 
OF 
LIUHT. 

Ag 

Hg 

Cu 

Pb 

PbCl2 

White. 

Slightly—  Freely. 

Insol. 



In  what  respects  are  the  chlorides  of  Ag,  Hg2 ,  and  Pb 
alike  ?  In  what  respects  do  the  chlorides  of  Hg  and  Cu 
differ  from  the  other  three  ? 

In  what  respects  do  the  two  chlorides  of  mercury  differ  ? 
Can  you  find  out  whether  a  given  solution  contains  a  com- 
pound of  Hg2  ? 

If  a  solution  contains  all  these  metals  in  the  form  of 
nitrates,  by  what  reagent  can  you  precipitate  the  Ag,  Hg2 , 
and  Pb  in  the  form  of  chlorides,  and  leave  the  others  in 
solution  ? 

Having  a  precipitate  consisting  of  chlorides,  how  can  you 
learn  whether  PbCl2  is  present  ?  By  what  reagent  can 
you  decide  whether  Hg2  C12  is  present  in  such  a  precipitate  ? 


108         LABOEATOliY  STUDIES   IN   CHEMISTRY. 


X.     TIN    (Sn). 


EXPERIMENT   118. 

Object.  —  To  study  the  reaction  of  tin  with  hydrochloric  acid. 

Manipulation  and  Notes.  —  Place  5  cc.  of  strong  hy- 
drochloric acid  in  a  test  tube,  and  drop  into  it  a  piece  of 
granulated  tin.  Then  heat  until  the  effervescence  is  brisk  ; 
after  which  keep  the  tube  warm  by  holding  it  above  the 
flame  of  the  lam]),  until,  when  taken  away  from  the  heat, 
the  bubbling  nearly  or  quite  stops.  If,  before  this  occurs, 
the  tin  is  used  up,  another  piece  must  be  added.  When  the 
effervescence  is  brisk,  test  the  escaping  gas  with  a  match 
flame. 

What  gas  is  set  free  by  the  action,  and  into  what  com- 
pound is  the  tin  changed  ?  Write  the  reaction. 

EXPERIMENT  119. 

Object.  —  To  ascertain  the  effect  of  nitric  acid  on  the  solution 
of  tin  chloride  obtained  in  the  previous  experiment. 

Manipulation  and  Notes.  —  (a)  Pour  about  2  cc.  of 
the  SnCl2  solution  into  another  tube,  add  four  or  five  drops 
of  strong  nitric  acid,  and  boil  the  mixture  a  minute.  Is 
there  any  evidence  of  a  chemical  change  ? 

(7>)  Prove  that  a  chemical  change  lias  or  has  not  been 
made  by  the  HNO3.  Tins  may  be  done  by  trying  the 
liquid  with  mercuric  chloride  before  and  after  boiling  with 
HN03.  Identical  results  would  show  that  no  change  had 
been  produced. 

Prepare  two  clean  tubes  with  10  cc.  of  water  in  each,  and 


TIN.  109 

add  to  one  about  1  cc.  of  the  solution  l  of  the  tin  chloride 
of  Exp.  118,  and  to  the  other  about  as  much  of  the  solution 
after  its  treatment  with  HNO3  in  Exp.  119.  Next  add  a 
drop  of  a  solution  of  mercuric  chloride  to  the  first  (note). 
Add  drop  by  drop  more  mercuric  chloride  (note). 

Now  add  to  the  other  solution  drops  of  mercuric-chloride 
solution  in  the  same  way  (note). 

From  these  results  you  can  judge  whether  the  tin  chloride 
was  changed  by  the  HN03. 

Is  it  still  a  chloride  ?  To  answer  this  question,  test  a 
portion  of  the  solution  with  AgN03,  and  add  NH4OH, 
Exp.  38  (a)  (c) . 

General.  —  The  foregoing  work  should  reveal  the  fact 
that  tin  is  capable  of  yielding  two  chlorides.  We  have 
stannous  chloride  (8iiCl2)  and  stannic  chloride  (SnCl4). 
Mercuric  chloride  enables  us  to  distinguish  one  from  the 
other,  as  it  is  reduced  to  gray  mercury  by  the  former  only. 
This  twofold  character  of  tin  is  general ;  there  are  two 
classes  of  tin  compounds. 

EXPERIMENT   12O. 

Object.  —  To  precipitate  and  study  the  properties  of  the  tin 
sulphides. 

1.    To  PRECIPITATE  THE  SULPHIDES. 

Manipulation  and  Notes To  10  cc.  of  water  add  \  cc. 

of  the  stannous  chloride  obtained  in  Exp.  118  ;  and  again,  to 
10  cc.  of  water  add  \  cc.  of  the  stannic  chloride  of  Exp.  119. 
Then  pass  hydrogen  sulphide  through  both  to  saturation 
(note). 

The  first  gives  stannous  sulphide  (SnS). 

The  second  gives  stannic  sulphide  (SnS2). 

1  A  white  precipitate  may  appear  at  this  point.  If  so,  the  addi- 
tion of  a  little  HC1  will  dissolve  it.  If  the  solution  already  contains 
sufficient  excess  of  H  Cl,  the  precipitate  will  not  appear. 


110        LABORATORY  STUDIES  IN  CHEMISTRY. 

2.    To  DISCOVER  SOME  PROPERTIES  OP  TIN 
SULPHIDES. 

Manipulation  and  Notes.  —  (a)  Obtain  the  clean  sul- 
phides for  examination.  To  do  this,  follow  the  directions 
found  in  Exp.  103  (/). 

Note  their  marked  difference  in  color,  and  recall  other 
sulphides  which  they  resemble. 

(b)  Are  these  sulphides  soluble  in  HC1?    Exp.  103  (/). 

(c)  Are  these  sulphides  soluble  in  HNO3  ? 

(d)  Are   these   sulphides   soluble   in   yellow  ammonium 
sulphide  ? 

General.  —  If  a  given  solution  contains  a  compound  of 
copper  or  of  tin,  how  will  you  convert  that  compound  into 
a  sulphide  ?  Will  the  sulphide  remain  in  solution,  or  be 
obtained  as  a  precipitate  ?  Why  ?  Can  you  judge  by  its 
appearance  whether  it  is  a  copper  sulphide  or  a  tin  sul- 
phide ?  Can  you  decide  with  certainty  ? 

EXPERIMENT  121. 

Object.  —  To  study  the    reaction  of  soluble   tin  compounds 

with  ammonium  hydroxide. 

Manipulation  and  Notes.  —  Use  solutions  of  (a)  stan- 
nous  chloride  made  in  Exp.  118  ;  (b)  stannic  chloride  made 
in  Exp.  119  (a).  Follow  directions  found  in  Exp.  96. 


ARSENIC,   ANTIMONY,    BISMUTH.  Ill 


XI.     ARSENIC    (As),  ANTIMONY    (Sb), 
BISMUTH  (Bi). 


EXPERIMENT   122. 

Object. —  To  obtain  clear  solutions  of  compounds  of  these 
metals,  for  use  in  the  study  of  their  reactions. 

Manipulation  and  Notes.  —  Put  20  cc.  of  water  into 
each  of  three  tubes.  Into  one,  a,  put  a  few  small  granules 
of  arsenious  oxide  (As2  03),  and  heat  (note).  Into  a  second, 
b,  put  a  few  drops  of  antimony  chloride  (SbCl3)  (note).  Into 
the  third,  c,  put  a  few  grains  of  bismuth  nitrate  (Bi  (N03)2) 
(note). 

Next  add  HC1,  drop  by  drop,  to  each  (note).  Which 
compound  is  soluble  in  water  ?  Which  are  decomposed  by 
water  ?  Which  are  soluble  in  acid  water  ? 

EXPERIMENT   123. 

Object.  —  To  precipitate  and  study  the  properties  of  the 
sulphides  of  these  metals. 

1.    To  PRECIPITATE  THE  SULPHIDES. 

Manipulation  and  Notes.  —  Proceed  with  the  solu- 
tions just  obtained  (Exp.  122),  treating  each  separately 
with  H2S,  as  in  previous  cases.  To  save  time,  study  the 
character  of  one  of  the  sulphides  while  another  is  being 
precipitated  (note). 

2.    To  STUDY  THE  CHARACTERS  OF  THESE  SULPHIDES. 

Manipulation  and  Notes.  —  Follow  the  plan  outlined 
for  the  study  of  tin  sulphide  (Exp.  120,  2) 

of  mT**4>5 


112        LABORATORY  STUDIES  IN   CHEMISTRY. 

may  be  written  out  for  each  separately,  as  usual ;  or  they  may 
be  tabulated  as  follows.  Prepare  a  skeleton  table  as  shown, 
and  fill  in  the  facts,  stated  in  brief,  when  discovered. 

Comparison  of  Sulphides  of  As,  Sb,  Bi. 


SULPHIDES. 

COLOK. 

IN  H  Cl 

IN  IINO3 

IN  (NH4)2S 

As2S3 

Sb2S3 

Bi2S3 

Put  the  formulas  of  the  tin  sulphides  in  the  table,  below 
Bi2S3;  fill  the  blanks  opposite;  compare  these  sulphides 
with  those  of  arsenic,  antimony,  and  bismuth,  and  note  the 
resemblances  and  differences. 

General.  —  The  foregoing  work  should  have  revealed  the 
close  general  resemblance  between  the  compounds  of  As,  Sb, 
and  Bi,  and  of  their  reactions ;  also  some  marked  differences 
in  details.  By  these  differences  you  would  be  able  to  dis- 
tinguish one  from  another  (explain). 

EXPERIMENT  124. 

Object.  —  To  study  the  action  of  nascent  hydrogen  on  arsenic 
trioxide. 

Manipulation  and  Notes.  —  To  liberate  the  H,  put  pure, 
zinc  and  water  into  a  bottle  generator  (Fig.  13,  p.  23).  To 
dry  the  gas  produced,  attach  a  calcium  chloride  tube  to  the 
delivery  tube  of  the  bottle,  and  to  this  attach  a  hard  glass 
tube  drawn  to  a  small  opening  at  the  other  end.  Pour  dilute 
sulphuric  acid  into  the  bottle  until  effervescence  occurs. 
Let  the  gas  drive  all  the  air  out  of  the  apparatus.  Then 
fire  the  jet  of  H,  and  observe  the  flame  (note).  Pour  a  very 


ABSENIC,   ANTIMONY,   BISMUTH. 


113 


little  solution  of  arsenic  trioxide  in  dilute  hydrochloric  acid 
into  the  bottle.  Observe  the  flame  (note).  If  it  is  a  flame 
of  H,  then  water  is  the  only  product ;  but  hold  a  cold  piece  of 
white  porcelain  across  its  tip  (note).  The  deposit  is  arsenic. 
Hence  the  burning  gas  must  be  the  compound  of  arsenic 
and  hydrogen  (As  H3)  produced  by  the  action  of  nascent 
H  on  the  As203.  This  is  a  delicate  test  for  arsenic 
(Marsh's). 

C.    EXERCISE  IN  COLLECTING  AND  TABULATING 
RESULTS  OF  EXPERIMENTS. 

Object.  —  To    compare    the   sulphides    of  mercury,    copper, 

lead,  cadmium,  zinc,  tin,  and  bismuth. 
Prepare  a  skeleton  table  like  that  below.     Fill  the  blanks 
by  consulting  your  notes  as  directed  in  Exercise  A,  p.  94. 

Table :  Comparison  of  Properties  of  some  Sulphides. 


METALS. 

SUL- 
PHIDES. 

COLOR. 

SOL'Y  IN 
H2O 

SOL'Y  IN 
IINO3 

SOL'Y  IN 
II  Cl 

SOL'Y  IN 

(NH4),  S 

Hg 

Hg  S 

Cu 

Pb 

Cd 

Zu 

Bi 

In  what  respect  does  the  ZnS  differ  from  all  the  others  ? 
In  what  respect  do  the  tin  sulphides  differ  from  the 
others  ? 


114         LABORATORY   STUDIES  IN   CHEMISTRY. 


XII.     ALUMINUM   (Al). 


EXPERIMENT  125. 

Object.  —  To  ascertain  whether  an  aluminum  compound 
in  solution  will  be  changed  to  a  chloride  by  hydrochloric 
acid. 

Manipulation  and  Notes.  —  Prepare  20  to  30  <r.  of 
solution  of  alum  (K2  A12  (SO4)4  -f  24H20).  Add  HC1  until 
the  acid  is  in  excess  (explain).  Then  evaporate  the  solu- 
tion to  crystallization.  Pour  the  liquid  away,  and  rinse 
the  crystals  with  water  to  remove  all  trace  of  HC1.  Com- 
pare the  product  with  the  alum.  Is  any  chemical  change 
visible  ? 

You  can  decide  whether  the  product  is  still  a  sulphate 
by  treating  its  solution  with  drop's  of  HC1  followed  by 
BaCl2  (Exp.  48);  or  whether  it  is  a  chloride,  by  AgN03 
followed  by  NH4OH  (Exp.  38).  Note  your  conclusion. 

The  use  of  other  soluble  compounds  of  Al  would  lead  to 
the  same  conclusion. 

EXPERIMENT  126. 

Object. —  To  ascertain  whether  an  aluminum  compound  in 

solution  will  be  changed  by  ammonium  hydroxide. 
Manipulation  and  Notes.  — Make  a  dilute  solution  of 
alum  in  H20,  and  add  NH4OH  little  by  little  to  excess 
(note).  Aluminum  hydroxide  (A12(HO)6)  is  white;  as  a 
precipitate,  it  is  gelatinous.  Is  it  insoluble  in  water  ?  If 
so,  it  must  have  appeared  with  the  addition  of  the  first 


ALUMINUM.  115 

drops  of  NH4OH.  Is  it  insoluble  in  cold  NH4OH?  If 
so,  it  did  not  disappear  when  NH4  OH  was  added  in  excess. 
Is  it  soluble  in  HC1?  Try  it  (note).  Is  it  soluble  in 
KOH?  Try  it  (note). 

EXPERIMENT  127. 

Object.  —  To  learn  whether  an  aluminum  compound  in  solu- 
tion is  affected  by  sodium  hydroxide. 

Manipulation  and  Notes.  —  To  a  dilute  solution  of 
alum  in  water  add,  drop  by  drop,  a  dilute  solution  of  so- 
dium hydroxide  (note).  Add  the  hydroxide  to  excess  (note). 
Can  you  explain  the  changes  ?  How  does  this  action  of  the 
NaOH  differ  from  that  of  NH4OH  (Exp.  126)  ? 

EXPERIMENT  128. 

Object.  —  To  learn  the  effect  of  heat  on  alum. 

Manipulation  and  Notes.  —  Put  a  few  crystals  of  alum 
that  seem  to  be  dry  into  a  dry  tube,  and  heat  them  slowly 
(note).  What  seems  to  condense  in  the  upper  part  of  the 
tube  ?  Continue  the  heat  (note).  Can  you  boil  the  alum 
all  away  ?  That  which  escaped  was  water,  .which  is  a 
necessary  constituent  of  the  crystals.  It  is  called  ivater 
of  crystallization. 

Use  gypsum.  See  if  you  can  detect  its  water  of  crystalli- 
zation. If  you  can  drive  it  all  off,  you  will  obtain  plaster 
of  Paris. 

Some  substances  lose  their  water  of  crystallization  on 
exposure  to  air.  Try  bright  crystals  of  sodium  sulphate. 
This  change  is  called  efflorescence. 


116        LABORATORY   STUDIES  IN   CHEMISTRY. 


XIII.     CHROMIUM    (Cr). 


EXPERIMENT  129. 

Object.  —  To  observe  the  change  which  may  occur  when 
a  soluble  chromium  salt  is  treated  with  an  alkaline 
hydroxide. 

Manipulation  and  Notes.  —  (a)  Use  the  double  sul- 
phate of  K  and  Cr  (KCr(S04)2  +  12  H2O)  known  as  chrome 
alum.  Dissolve  a  small  quantity  in  water,  and  add  NH4  ( )H 
little  by  little  (note)  to  excess  (note).  The  visible  product 
is  Cr2(HO)6.  Is  it  soluble  in  cold  NH4OH  ?  Is  it  soluble 
in  hot  NH4  OH  ?  Let  there  be  large  excess,  and  heat  it 
just  to  boiling.  Let  the  precipitate  settle,  and  note  the 
color  of  the  liquid.  Boil  the  liquid  in  a  porcelain  dish 
for  several  minutes  (note). 

(b)  To  another  solution  of  the  chrome  alum  add  drops  of 
KOH  (note),  then  more  KOH  to  excess  (note).     Compare 
the  color  of  this  solution  with  that  obtained  by  NH4  OH. 

Write  the  reaction  for  the  Cr2  (H(  ))6  in  (a) ;  also  the  re- 
action for  the  hydroxide  in  (b).  Does  the  same  hydroxide 
seem  to  be  produced  by  the  two  alkalies  ? 

General.  —  The  different  colors  of  the  two  solutions  of 
the  same  hydroxide  suggest  that  there  are  two  forms  or 
varieties  of  this  hydroxide,  —  the  violet  and  the  green.  In 
this  respect  the  hydroxide  in  solution  is  typical  of  the 
chromium  salts.  There  are  two  modifications,  —  the  violet 
and  the  green. 

(c)  Is  the  Cr2  (H0)6  soluble  in  NH4C1  ? 


CHROMIUM.  117 

EXPERIMENT  13O. 

Object.  —  To  study  the  change  which  may  occur  when  a 

soluble  chromium  salt  is  treated  with  (NH4)2S. 
Manipulation  and  Notes.  —  Use  the  solution  of  a  little 
chrome  alum  in  water.  Add  the  (NH4)2S  little  by  little, 
to  excess  (note).  Compare  the  precipitate  with  the  hydrox- 
ide in  Exp.  129  (note).  Is  it  a  sulphide  or  the  hydroxide  ? 
Try  to  prove  that  it  is  not  a  sulphide  (explain).  Compare 
Exp.  128. 

EXPERIMENT  131. 

Object.  —  To  study  the  effect  of  a  strong  oxidizing  agent  on 
a  solid  chromium  salt. 

Manipulation  and  Notes.  —  Use  chrome  alum,  and 
oxidize  it  by  fusion  with  KN03  as  follows.  Make  a  little 
mixture  of  powdered  KNO3  and  powdered  Na2C03,  and 
add  a  very  little  powdered  chrome  alum.  Put  the  mixture 
on  a  piece  of  broken  porcelain  dish,  or,  better,  platinum 
foil.  Hold  this  support,  with  forceps,  in  the  top  of  the 
Bunsen  flame,  and  heat  it  gradually  until  the  mixture 
melts.  Keep  it  melted  for  some  time,  and  then  let  it  cool. 

If  the  fusion  has  been  successful,  the  color  of  the  fused 
mass  may  give  some  evidence  of  chemical  change  (note). 
Boil  the  fused  mass  in  a  small  quantity  of  water ;  filter 
the  solution;  and,  if  its  color  is  not  distinct,  evaporate  it 
down  to  smaller  bulk.  Does  it  seem  to  contain  either  the 
violet  or  green  chromium  salt  ?  Test  a  little  of  it  with 
NH4OH  (Exp.  129).  Does  it  act  like  a  chromium  salt? 
Obtain  a  little  solution  of  potassium  chromate.  Does  your 
product  resemble  this  ? 

General.  —  This  experiment  should  illustrate  the  power 
of  strong  oxidizing  agents  to  change  Cr  from  the  basic 


118         LABORATORY  STUDIES  IN   CHEMISTRY. 

to  the  acid  part  of  its  salts.  In  chromium  sulphate 
(Cr2  (S04)3),  Or  is  the  basic  element ;  in  potassium  chro- 
mate  (K2O04),  potassium  is  the  basic  element,  while 
chromium  is  in  the  acid  radical.  These  two  salts  are 
types  of  two  large  classes  of  chromium  compounds. 

EXPERIMENT   132. 

Object  —  To  learn  the  effect,  if  any,  of  oxidizing  agents 
on  potassium  cJiromate. 

Manipulation  and  Notes.  —  Make  a  solution  of  K2  Or  O4 
in  water.  Divide  it  into  two  portions,  and  add  HN03  to 
one  (note).  Judge  by  the  color  whether  chemical  change 
occurs.  Then  evaporate  both  solutions  to  crystallization. 
Compare  the  crystals.  The  new  salt  is  potassium  diehro- 
mate  (K2Cr207). 

General.  —  These  two  potassium  chromates  are  typical 
of  two  classes  of  chromates,  —  the  yellow  normal  cJtromatet, 
and  the  orange  red  dichromates  ;  and  the  yellow  salts  are 
easily  changed  into  the  red  by  an  oxidizing  agent. 

EXPERIMENT  133 

Object.  —  To  observe  the  effect,  if  any,  of  hydrochloric  acid 

and  hydrogen  sulphide  on  a  solution  of  a  dichromate. 
Manipulation  and  Notes.  —  Add  a  little  H  Cl  to  a 
solution  of  K2Cr207  (note).  Heat  the  mixture  to  boiling 
(note).  Then  pass  H2  S  into  the  hot  solution  (note).  You 
can  judge  by  the  color  whether  the  liquid  now  contains  the 
dichromate,  a  normal  chromate,  or  a  chromium  salt. 

K2  Cr2  O7  +  8 II  Cl  +  3 II2  S  =  2  K  01  +  7 IT2  O  +  Cr.2  Cle  +  S3. 

Did  you  see  any  free  S  in  the  liquid  ?  What  became  of 
theH  of  theH2S? 


CHROMIUM.  119 

General.  —  This  experiment  illustrates  the  fact  that  a  di- 
chromate  is  reduced  to  a  Cr  salt  by  the  action  of  substances 
whose  elements  have  strong  affinity  for  0,  as  the  H  in  H2  S 
has  :  in  other  words,  by  reducing  agents. 

EXPERIMENT  134. 

Object.  — To  observe  tJie  effect  of  ammonium  sulphide  on  a 
dicltromate. 

Manipulation  and  Notes.  —  To  a  solution  of  K2  Cr2  07 
in  a  tube  add  a  little  (NH4)2S  (note).  The  change  in 
color  may  help  you  to  judge  what  change  occurred  in  the 
dichromate. 

EXPERIMENT   135. 

Object.  —  To  become  acquainted  with  the  behavior  of  a,  solid 
compound  of  chromium  w lien  fused  ivith  borax. 

Manipulation  and  Notes.  —  Insert  the  platinum  wire 
loop  (Fig.  33,  p.  85),  when  hot  or  moistened,  'into  powdered 
borax,  and  fuse  the  adhering  borax  in  the  blowpipe  or 
Bunsen  flame.  Repeat  until  the  loop  is  filled  with  a  trans- 
parent bead.  Moisten  the  clear  cold  bead,  and  touch  it  to 
a  very  little  of  the  powdered  given  solid.  Now  melt  the 
substance  into  the  bead  by  means  of  the  outer  or  oxidizing 
blowpipe  flame,  and  note  the  color  of  the  bead  while  hot, 
and  after  it  has  become  cold.  Is  the  solid  dissolved  in  the 
bead  ?  Is  the  bead  distinctly  colored  ? 

Fuse  the  bead,  containing  the  substance,  in  the  inner  or 
reducing  blowpipe  flame  (note). 


120        LABORATORY  STUDIES  IN   CHEMISTRY. 


XIV.     MANGANESE  (Mn). 


EXPERIMENT   136. 

Object.  — To  study  the  chantje  which  may  occur  when  a 
manganous  salt  Is  treated  with  an  alkaline  hydroxide. 

Manipulation  and  Notes.  —  (a)  Use  the  manganous 
chloride  (Mn  C12)  or  the  niaiigaiious  sulphate  (Mn  S()4). 
Dissolve  in  water,  and  treat  the  solution  with  NH4()H,  as 
in  Exp.  129  (a)  (note)]  and  with  KOH,  tis  in  Exp.  129  (b) 
(note).  Note  any  change  in  the  color  of  the  product  taking- 
place  at  once  or  on  standing. 

(b)  Will  the  action  of  the  hydroxide  NH4()H  be  affected 
by  the  presence  of  NH4  Cl  ?  Try  it.  Use  large  proportion 
of  NH4C1.  Let  this  mixture  stand  (note). 

EXPERIMENT   137. 

Object. —  To  convert  any  soluble  s<tlt  of  nutnganese  into  the 
sulphide. 

Manipulation  and  Notes.  —  (a)  Add  (NH4)»  S  little  by 
little  to  a  solution  of  the  manganese  salt  (note).  Study  the 
reaction.  Is  the  product  a  sulphide,  or  is  it  an  hydroxide  ? 
Expose  the  freshly  made  product,  on  a  niter,  to  the  air  for 
some  time  (note).  Ascertain  whether  this  sulphide  is  solu- 
ble in  NH401. 

General.  —  The  foregoing  experiments  reveal  the  be- 
havior of  manganous  compounds  toward  the  reagents  used, 
and,  by  comparison,  the  general  resemblance  of  Mn  to  Cr  in 
these  reactions  (ex  plain).  The  special  differences,  also,  are 
apparent  (explain). 


MANGANESE.  121 

They  also  reveal  the  fact  that  the  maiiganous  hydroxide 
and  sulphide  change  color  on  exposure  to  air.  This  is  true 
of  a  few  other  manganous  compounds.  They  are  oxidized 
by  the  air.  Mn  (OH)2  is  oxidized  to  Mn2  (OH)6 ;  and  this 
manganic  hydroxide  is  the  type  of  a  class,  —  the  manganic 
compounds. 

EXPERIMENT   138. 

Object.  —  To   stud?/   the  effect  of  more  energetic   oxidizing 
agents  on  manganous  compounds. 

Manipulation  and  Notes.  —  Eeduce  the  compound  (say 
dry  Mn(HO)2)  to  a  fine  powder,  and  use  KN03  as  the  oxi- 
dizing agent.  Proceed  as  directed  in  Exp.  131  to  oxidize 
by  fusion  with  KjST03  and  Na2C08.  Use  the  greatest  heat 
you  can  command,  but  do  not  let  the  flame  itself  touch  the 
mixture.  (Hot  illuminating  gas  is  a  reducing  agent.)  The 
tip  of  a  blowpipe  flame  against  the  under  surface  of  plati- 
num foil  may  be  used  in  preference  to  the  Bunsen  flame. 
Note  the  change  in  color  which  betrays  the  oxidation.  If 
the  color  is  not  the  same  as  that  already  obtained  by  oxi- 
dation in  Exp.  137,  it  suggests  a  different  product  (note). 
Dissolve  when  cold  in  a  small  quantity  of  cold  water,  and 
filter  the  solution  (note).  Keep  it. 

General.  —  In  this  experiment  you  produce  potassium 
manganate  (K2M~n04).  Manganese  is  no  longer  the  basic 
element :  it  has  become  acidic.  Compare  with  oxidation  of 
chromium,  Exp.  131.  In  the  same  way  other  manganous 
salts  are  changed  to  manganates. 

EXPERIMENT  139. 

Object.  —  To  ascertain  whether  ]wtassium  manganate,  like 
potassium  chromate,  may  be  oxidized  still  further. 

Manipulation  and  Notes.  —  Use  the  solution  obtained 
in  the  preceding  experiment,  or,  better,  a  larger  quantity 


122         LAHORATOIiY   STUDIES   IN   CHEMISTRY. 

made  by  dissolving  the  salt  in  water.  Boil  this  solution 
(note).  The  change  in  color  betrays  the  oxidation  of 
K2Mn04  to  K2Mn208  (potassium  permanganate). 

3  K.2Mn  O4+2  H2O  =  K2  Mn,  O8  +  Mn  <X+4  KOH. 
What  is  the  oxidizing  agent  in  this  case  ? 

EXPERIMENT  14O. 

Object.  —  To  ascertain  whether  potassium  permanganate  is 

easily  reduced,  and,  if  so,  to  what  condition. 
Manipulation  and  Notes.  —  (a)  To  10  cc.  of  water  add 
potassium  permanganate  enough  to  color  it  very  distinctly, 
then  a  little  KOH,  and  boil  the  mixture  (note).  Judge  by 
the  color  what  compound  is  formed  by  the  reduction  of 
Ko  Mn2  08. 

(b)  To  a  very  dilute  solution  of  K2Mn208,  first  add  a 
little  sugar,  then  KOH,  and  boil  the  mixture  (note).     To 
what  condition  is  the  K2Mn208  now  reduced  ? 

(c)  Put  a  little   sugar   alone  with  the  dilute  K2Mn2O8, 
and  boil  it  more  persistently  (note). 

General.  —  The  sugar  represents  other  substances  whose 
elements  have  strong  attraction  for  oxygen.  P>y  these  the 
K2Mn208  is  reduced  beyond  the  green  K2Mn04to  lower 
compounds,  which  are  brown. 

EXPERIMENT  141. 

Object.  —  To  become  acquainted  with  fhe  behavior  of  man- 

yanese  compounds  in  the  "boras  bead." 
Manipulation   and  Notes.  —  Proceed    as   with   Cr   in 
Exp.  135. 


IKON.  123 


XV.    IRON  (Fe). 


EXPERIMENT  142. 

Object.  —  To  study  the  reactions  of  ferrous  and  ferric  com- 
pounds with  an  alkaline  hydroxide. 

Manipulation  and  Notes.  —  Prepare  two  tubes,  —  one 
with  a  dilute  solution  of  ferrous  chloride  (FeCL),  the 
other  with  a  dilute  solution  of  ferric  chloride  (Fe2Cl<;). 
To  the  first  add  a  little  NH4OH  (note),  then  to  excess 
(note).  Treat  the  second  in  the  same  way.  Pour  the  first 
upon  a  filter  to  be  examined  afterward. 

Write  and  explain  the  reaction  in  each  case.  Mark  the 
differences  of  the  two  hydroxides  in  appearance  and  com- 
position. They  are  typical  differences  of  the  ferrous  and 
ferric  compounds  generally. 

Examine  the  hydroxide  left  on  the  filter  (note).  Explain 
the  change.  Ascertain  whether  NH4C1  will  prevent  the 
precipitation  of  these  hydroxides. 

EXPERIMENT  143. 

Object. —  To  study  the  reaction  of  soluble  iron  compounds 

with,  ammonium  sulphide. 

Manipulation  and  Notes.  —  Prepare  two  tubes,  —  one 
with  a  dilute  solution  of  ferrous  chloride,  the  other  with  a 
dilute  solution  of  ferric  chloride.  To  the  first  add  drops 
of  (NH4).2S  (note).  Treat  the  second  in  the  same  way. 
Judging  by  appearances,  are  the  two  precipitates  the  same, 
or  different  substances  ?  Can  you  write  the  two  reactions 
on  the  hypothesis  that  the  two  are  the  same  substance? 
Ascertain  whether  tLis  sulphide  is  soluble  in  HC1. 


124        LABORATORY  STUDIES  IN  CHEMISTRY. 
EXPERIMENT  144. 

Object.  —  To  study  the  effect  of  oxidizing  agents  on  ferrous 
compounds. 

Manipulation  and  Notes.  —  (a)  Use  H  N03.  To  about 
5  cc.  of  water  acid  about  1  cc.  of  solution  of  FeClo  and  4  or 
5  drops  of  HN03.  Boil  the  mixture  gently  for  about  a 
minute.  The  change  in  color  should  indicate  the  change 
in  composition,  and  by  drops  of  NH4  OH  (as  in  Exp.  142) 
you  can  decide  whether  that  change  has  occurred. 

(b)  Use  K2  Mn2  O8 .  Acidulate  a  solution  of  ferrous  chlo- 
ride. Add  K2Mn2O8  (note)  until  its  color  can  be  just  de- 
tected in  the  liquid  (give  reason).  Some  indication  of  a 
change  in  the  Fe  C12  should  have  been  observed  during  the 
work.  Can  you  prove  that  the  FeCl2  has  been  changed  to 
Fe2016? 

EXPERIMENT  145. 

Object. —  To  study  the  action  of  reducing  agents  on  ferric 
compounds. 

Manipulation  and  Notes.  —  («)  Use  H2  S.  Acidulate 
a  solution  of  ferric  chloride  with  H  01.  Then  pass  H2  S 
gas  through  it  (note).  A  change  in  color  should  suggest 
the  chemical  change.  Can  you  prove  that  the  iron  has  been 
reduced  to  ferrous  form  ? 

Write  the  reaction  and  explain  it. 

(b)  Use  nascent  hydrogen.  The  H  may  be  liberated  by 
zinc  and  sulphuric  acid.  The  better  way  is  to  use  amal- 
gamated zinc  with  a  strip  of  platinum.  Thus  :  Clean  a  few 
pieces  of  granulated  zinc  by  immersion  in  dilute  H2S04. 
Amalgamate  them  by  contact  with  mercury.  Place  them 
in  a  test  tube,  and  put  a  piece  of  platinum  in  contact 
with  them.  Prepare  a  dilute  solution  of  ferrous  sulphate, 
its  color  visible.  Add  some  dilute  H2  S04  and  pour  it  upon 


IRON.  125 

the  Zn,  Close  the  tube  with  a  stopper  having  a  small 
hole  for  escape  of  gas,  to  cut  off  free  access  of  air  (give 
reason),  and  let  the  whole  stand  (note).  Finally  you  can 
decide  by  color  (explain)  and  test  (explain)  whether  the 
iron  remains  in  the  ferric  or  the  ferrous  form.  Write  and 
explain  the  reaction. 

EXPERIMENT  146. 

Object.  —  To  become  acquainted  with  another  test  by  which 
to  decide  whether  a  solution  contains  a  ferrous  or  a 
ferric  compound. 

Manipulation  and  Notes.  —  Try  to  convert  the  iron 
into  "  Prussian  blue  "  by  means  of  potassium  ferrocyanide. 
Prepare  two  tubes,  —  one  with  a  dilute  solution  of  a  ferric 
salt,  the  other  with  a  dilute  solution  of  a  ferrous  salt.  Acid- 
ulate each  with  a  drop  or  two  of  HC1.  To  the  first  add 
drops  of  potassium  ferrocyanide  (note).  Treat  the  second 
in  the  same  way  (note).  Mark  the  difference  in  the  products. 
The  first  is  the  "Prussian  blue." 

EXPERIMENT  147. 
Object.  —  To  become  acquainted  with  the  behavior  of  iron 

confounds  in  the  "  borax  bead." 

Manipulation  and  Notes.  —  Proceed  as  directed  in 
Exp.  135. 

D.     EXERCISE  IN  COLLECTING  AND  TABULATING 

RESULTS  OF  EXPERIMENTS. 
Object.  —  To  compare  the  properties  of  the  hydroxides  of 

zinc,  aluminum,  chromium,  manganese,  iron. 
Prepare  a  skeleton  table  like  that  on  p.  126.     Fill  the 
blanks  by  gleaning  the  facts  from  your  own  notes,  as  di- 
rected in  Exercise  A,  p.  94. 


126        LABORATORY  STUDIES  IN   CHEMISTRY. 

Table :  Comparison  of  Properties  of  some  Hydroxides. 


SOL'Y  IN 

SOL'Y  IN 

METALS. 

HYDROXIDES. 

COLOR. 

N1I4  OH 

N1UC1 

Zn 

Al 

Cr 

Mn 

A  given  solution  contains  a  compound  of  either  Zn  or  Al : 
how  would  you  decide  which  ? 

A  solution  contains  a  compound  of  either  Mn  or  Fe  :  how 
would  you  decide  which  ?  In  what  respect  does  the  Mn 
hydroxide  differ  from  the  Zn  hydroxide  ? 

A  solution  contains  a  compound  of  iron :  how  would  you 
decide  whether  it  is  a  ferrous  or  a  ferric  compound  ? 


NICKEL,    COBALT.  127 


XVI.    NICKEL   (Ni),   COBALT   (Co). 

EXPERIMENT  148. 

Object.  —  To  study  the  reactions  of  soluble  nickel  and  cobalt 
compounds  ivith  an  alkaline  hydroxide,  and  to  compare 
the  two  hydroxides. 

Manipulation  and  Notes.  —  (a)  To  a  dilute  solution 
of  the  given  salt  (use  the  sulphate)  add  NH4  OH  gradually 
(note)  to  excess  (note).  Compare  the  reactions  and  results 
obtained  with  Ni  and  Co  compounds.  Ascertain  whether 
the  hydroxide  is  soluble  in  NH4C1. 

(b)  Use  K  OH  instead  of  NH4  OH  in  the  same  way.  Note 
carefully  any  differences  in  the  results  with  compounds  of 
Ni  and  Co.  Note  also  any  differences  in  the  action  of  the 
two  alkaline  hydroxides  used.  Also  compare  the  hydroxides 
of  Ni  and  Co  with  those  of  Fe,  Mn,  Cr,  and  Zn. 

EXPERIMENT  149. 

Object.  —  To  convert  soluble  compounds  of  nickel  and  cobalt 
into  sulphides.,  and  to  compare  the  products. 

Manipulation  and  Notes.  —  Add  (NH4)2S  to  a  dilute 
solution  of  the  given  substance  (note).  Compare  these  two 
sulphides,  and  the  reactions  which  produced  them.  Ascer- 
tain whether  these  sulphides  are  soluble  in  HC1. 

General.  —  The  foregoing  experiments  should  reveal 
the  very  close  resemblance  of  compounds  of  Ni  and  Co,  in 
their  behavior  toward  the  reagents  used.  This  resemblance 
is  maintained  throughout  all  the  chemical  relations  of  these 
two  metals. 


128         LABORATORY  STUDIES   AY   CHEMISTRY. 


EXPERIMENT  15O. 

Object.  —  To  become  acquainted  with  the  potassium-cyanide 
test,  by  wliicli  to  decide  whether  a  f/iueu  solution  contains 
a  nickel  or  a  cobalt  compound. 

Manipulation  and  Notes.  —  (a)  Make  a  fresh  solution 
of  potassium  cyanide  (K  Cy)  in  water.  Add  this  in  small 
quantity  to  the  given  solution  (note).  Then  add  more  of 
the  KCy,  but  no  more  than  needed  to  complete  the  change 
(note).  Finally  add  HC1  (note).  Use  the  Ni  and  Co  sul- 
phates. 

(b)  Acidify  the  given  solution  with  several  drops  of 
acetic  acid.  Add  the  KCy  as  in  (a),  shaking  the  liquid. 
Boil  the  solution  for  same  time ;  let  it  cool ;  and  finally  add 
H  Cl  in  excess,  and  let  the  mixture  stand  for  some  time. 
Use  the  Ni  and  Co  sulphates. 

EXPERIMENT  151. 

Object.  —  To  become  acquainted  with  the  behavior  of  com- 
pounds of  nickel  and  cobalt  in  the  "borax  bead." 

Manipulation  and  Notes.  —  Proceed  as  directed  in 
Exp.  135. 

E.    EXERCISE  IN  COLLECTING  AND  TABULATING 
RESULTS  OF  EXPERIMENTS. 

Object.  —  To  compose   the  properties  of  the  sulphides  oj 

zinc,  manganese,  iron,  nickel,  cobalt,  copper,  tin. 
Prepare  a  skeleton  table  like  that  on  p.  129.     "Fill  thx. 
blanks  by  gleaning  the  facts  from  your  own  notes,  as  di 
rected  in  Exercise  A,  p.  94. 


NICKEL,    COBALT. 


129 


Table :  Comparison  of  Properties  of  some  Sulphides. 


METALS. 

SULPHIDES. 

COLOB. 

SOL'Y  IN 
HNO3 

SOL'Y  IN 
HC1 

SOL'Y  IN 
(NH4)2S 

Zn 

Mn 

Fe 

Ni 

Co 

Cu 

Sn 

In  what  respect  do  the  first  five  sulphides  in  this  table 
differ  from  the  last  two  ? 

If  a  solution  should  contain  all  these  metals  in  the  form 
of  chlorides,  by  what  reagent  would  you  precipitate  them 
all  in  the  form  of  sulphides  ?  Having  the  mixture  of  all 
these  sulphides,  by  what  solvent  could  you  separate  the  first 
five  from  the  last  two  ?  Having  the  last  two  only,  how 
could  you  separate  them  ? 


PART  III. 


APPLICATION    OP    CERTAIN     FOREGOING    RE- 
ACTIONS   TO    QUALITATIVE    ANALYSIS. 

I.     PKELIMINABY   STATEMENTS. 

THE  foregoing  study  of  the  chemical  characters  of  ele- 
ments and  compounds  has  shown  that  each  differs  from 
every  other  in  some  particulars,  but  that  in  other  respects 
several  may  be  much  alike. 

By  the  general  resemblances  between  certain  of  their 
compounds,  the  metals  may  all  be  placed  in  a  few  groups. 
By  the  specific  differences  of  these  same  or  other  compounds, 
the  individual  metals  in  a  group  may  be  identified. 

This  application  of  our  knowledge  of  general  chemistry 
to  determine  the  constituents  of  substances  wrhose  composi- 
tion is -unknown  to  us  is  of  the  highest  practical  value. 

You  should  now  try  to  collect  and  classify  the  facts 
which  you  have  discovered  in  order  that  you  may  use  them 
for  this  purpose;  that  is,  for  the  purpose  of  Qualitative 
Analysis. 

II.     THE   ANALYTICAL   CLASSIFICATION. 

The  grouping  of  the  metals  is  founded  upon  the  solubility 
of  a  few  classes  of  their  compounds. 

For  example  :  You  found  that  silver  chloride  is  insoluble 
in  water  (Exp.  105),  and  that  copper  chloride  is  soluble  in 

130 


THE  ANALYTICAL   GROUPS* 


131 


water  (Exp.  108).  For  this  reason  silvercmbritfe'^can  be 
precipitated  by  HC1,  while  copper  chloride  cannot  be. 

Now,  all  metals  whose  chlorides  are,  like  that  of  silver, 
insoluble  in  water,  may  be  put  with  silver  to  form  one 
group.  In  the  same  way,  metals  whose  sulphides  are  in- 
soluble may  form  another  group  ;  and  so  on  for  others. 

But  you  have  examined  the  solubility  of  a  large  number 
of  compounds,  and  the  facts  are  in  your  note-book.  If  you 
will  collect  and  tabulate  them,  you  will  have  the  analytical 
classification  as  a  result  of  your  own  investigation. 

Proceed  as  follows  :  Prepare  a  skeleton  table  with  six 
columns,  like  that  below,  and  fill  the  blanks  by  gleaning 
the  facts  from  your  own  notes.  In  each  column  write  the 
symbols  of  the  metals  whose  compounds  are  insoluble  as 
described  at  the  head  of  the  column  ;  but  omit  from  each 
column  those  already  placed  in  the  columns  before  it. 


III.     THE  ANALYTICAL  GROUPS. 


CHLORIDES 
INSOLUBLE 
IN  H2O 

AND  HC1 

SULPHIDES 
INSOLUBLE 
IN  H2O 

AND   H  Cl 

HYDROXIDES 
INSOLUBLE 
IN  NH4OH 

ANDNH4C1 

SULPHIDES 
SOLUBLE  IN 

H  Cl.     IN  SOL. 

IN  NH4  Oil 

CARBONATES 
INSOLUBLE 
IN  NH4C1 

AND  NH4  OH 

FOREGOING 
COMPOUNDS 
ALL  SOLUBLE 

IN   H2O. 

1.... 

1.... 

1.... 

1.... 

1.... 

1.... 

2.... 

2.... 

2.... 

2.... 

2.... 

2.... 

3.  ... 

3.... 

3.... 

3.... 

3.... 

3.... 

4.... 

4.... 

4.... 

5.... 

7.... 

GKOUP  T. 
Precipitated 
by  HC1 

GROUP  II. 
Precipitated 
byH2S 

GROUP  III. 
Precipitated 
byNH4OH 

GROUP  IV-. 
Precipitated 
by  (NH4)2  S 

GROUP  V. 
Precipitated 

(NH4)^C03 

GROUP  VI. 
not 
Precipitated 

132        LABORATORY  STUDIES  IN  CHEMISTRY. 

IV.     ANALYSIS  OF  A  SIMPLE  SALT. 
1.    To  FIND  WHAT  METAL  THE  SALT  CONTAINS. 

If  the  salt  is  in  the  solid  form,  you  first  dissolve  it.  For 
the  present  we  will  suppose  that  it  is  soluble  in  water. 

(a)  Is  this  salt  a  compound  of  a  metal  in  Group  1.  ?  To 
answer  this  question,  try  to  convert  it  into  a  chloride.  Put 
a  small  portion  of  the  strong  solution  into  a  tube,  and  add 
HG1  drop  by  drop.  If  a  precipitate  is  made,  it  must  be  a 
chloride  of  Ag,  Hg2,  or  Pb,  —  the  metals  of  Group  I.,— 
since  these  are  the  only  chlorides  insoluble  in  1I2O  and 
H  Cl ;  and  you  can  decide  which  it  is  by  the  different 
behavior  of  these  chlorides  toward  hot  water,  ammonium 
hydroxide,  and  light,  as  discovered  by  experiments  made  in 
the  study  of  these  metals. 

But  if  HC1  yields  no  precipitate,  you  judge  that  the  salt 
is  not  a  compound  of  Ag,  Pb,  or  Hg2. 

(/>)  Is  the  salt  a  compound  of  any  metal  hi  Group  II.  ? 
To  answer  this  question,  try  to  convert  it  into  a  sulphide. 
Treat  a  portion  of  the  diluted  solution,  which  has  been 
made  acid  by  drops  of  II  Cl,  with  H2S.  If  a  precipitate  is 
made,  it  must  be  a  sulphide  of  Hg,  Cd,  Cu,  Bi,  As,  Sb,  or 
Sn  (give  reason).  Proceed  to  ascertain  which  one  by  testing 
it  for  the  properties  in  which  those  sulphides  differ. 

You  have  learned  that  the  As,  Sb,  and  Sn  sulphides  are 
soluble  in  (NH4)2S  (Exps.  123,  2;  and  120,  2,  r7),  while  th<> 
other  four  sulphides  are  not.  Hence  proceed  as  directed  in 
Exp.  123,  2  (&),  (d),  and  you  can  decide  whether  the  metal 
of  the  salt  is  one  of  the  three,  As,  Sb,  Sn ;  or  one  of  the 
four,  Hg,  Cd,  Bi,  Cu. 

Having  decided  this,  you  can  proceed  to  identify  the 
metal  by  experiments  which  you  made  in  the  study  of 
these  metals. 


ANALYSIS   OF  A   SIMPLE  SALT.  133 

But  if  H2  S  yields  no  precipitate,  you  are  ready  to  declare 
that  the  salt  is  not  a  compound  of  any  one  of  these  seven 
metals  (give  reason). 

(c)  Is  the  salt  a  compound  of  any  metal  in  Group  III.  ? 
To  answer  this,  try  to  convert  it  into  an  hydroxide.     Use  a 
portion  of  the  original  solution.     Add  considerable  NH4  Cl,1 
and  then  add  NH4OH   by  drops  until  the  liquid  smells 
strongly  of  this  substance.1      Do  not  mistake  the  odor,  of 
the  air  above  the  liquid  for  that  of  the  liquid.     If  a  pre- 
cipitate is  made  in  this  way,  it  must  be  an  hydroxide  of 
Or,  Al,  or  Fe  (give  reason)  ;  and  you  ascertain  which  one 
by  experiments  which  you  made  when  studying  the  char- 
acter of  these  metals. 

But  if  no  precipitate  is  obtained  by  NH4OH,  you  infer 
that  the  salt  is  not  a  compound  of  any  one  of  these  metals. 

(d)  Is  the  salt  a  compound  of  any  metal  in  Group  I V.  ? 
To  answer  this,  try  to  convert  it  into  a  sulphide  in  presence 
of  NH4OH.      For  this   purpose  you  can  use  the  solution 
already  in  hand,  containing  NH4C1  and  NH4OH,  or  you 
can  add  these  reagents  to  a  portion  of  the  original  solution. 

Add  (NH4)2S.  If  a  precipitate  appears,  it  must  be  a 
sulphide  of  Zn,  Mn,  Ni,  or  Co  ((jive  reason),  and  you  can 
decide  which  by  noting  the  differences  in  these  sulphides 
and  by  experiments  made  in  the  study  of  these  metals. 

But  the  absence  of  a  precipitate  is  evidence  that  the  salt 
is  not  a  compound  of  any  one  of  these  metals. 

(e)  Is  this  salt  a  compound  of  any  metal  in   Group  V.  ? 
To  decide  this  question,  try  to  convert  it  into  a  carbonate. 
Use  a  portion  of  the  original  solution.     Add  considerable 
NH4C1  (give  re,ason),  and  then  (NH4)2C03.    If  a  precipitate 
appears,  it  must  be  a  carbonate  of  Ba,  Sr,  or  Ca  (give  rea- 

1  For  the  object  of  adding  NH4C1  here  and  in  future  operations, 
see  Exp.  92  (<•) ;  and  Exp.  136  (b).  For  the  object  of  using  "  excess  " 
of  NH4  OH,  see  Exp.  96. 


134         LABORATORY  STUDIES  IN  CHEMISTRY. 

son),  and  you  can  decide  which  one  by  the  differences  in 
their  reactions  discovered  by  Exp.  93  (a)  and  (b). 

But  if  no  precipitate  appears,  no  compound  of  any  one  of 
these  metals  can  be  present,  and  you  must  conclude  that 
the  salt  is  a  compound  of  one  of  the  metals  in  Group  VI. 

(/)  Which  one  of  the  four  ?  To  ascertain  which,  you 
may  in. ike  Exps.  88  and  89. 

2.    To  FIND  WHAT  ACID  RADICAL  THE  SALT  CONTAINS. 

The  next  object  is  to  learn  whether  the  salt  is  a  chloride, 
a  nitrate,  or  some  other  compound  of  the  metal.  Bui;  the 
characteristic  reactions  of  these  classes  of  salts  have  been 
revealed  by  your  study  of  them  in  Part  I.  Thus,  you  can 
identify  a  chloride  by  Exp.  38 ;  a  sulphate,  by  Exp.  48 ;  a 
nitrate,  by  Exp.  67 ;  a  carbonate,  by  Exp.  72 ;  and  others, 
by  experiments  made  in  the  course  of  your  work. 

Having  found  the  metal  in  the  salt,  and  its  acid  radical, 
you  can  announce  the  name  of  the  substance. 

For  practice  in  the  analysis  of  simple  salts,  you  should 
receive  substances  from  the  instructor.  Follow  the  fore- 
going general  directions,  but  at  the  same  time  consult  a  good 
book  on  qualitative  analysis  for  information  which  the  fore- 
going studies  have  not  been  carried  far  enough  to  impart. 

3.    HINTS  .IN  REGARD  TO  NOTES. 

In  this  work  your  notes  should  be  kept  faithfully  and 
systematically.  They  should  contain  a  brief  account  of 
every  step  and  the  inference  drawn  from  it.  Every  step 
that  goes  wrong,  no  less  than  those  which  seem  to  go  right, 
should  be  recorded,  witli  the  cause  of  the  failure,  if  you 
can  discover  it.  Never  discard  an  experiment  nor  "  begin 
over  "  unless  you  can  give  a  good  reason  for  doing  so.  At 
the  end  of  the  analysis,  your  notes  should  be  handed  to  the 
teacher  as  your  "  Report "  on  the  work. 


ANALYSIS  OF  A   COMPLEX  SUBSTANCE.      135 


One  good  form  in  which  to  keep  these  notes  is  given 
below.  It  is  the  "three-column"  system.  Do  not  forget 
to  head  the  sheet  with  your  name,  the  date,  and  the  desig- 
nation of  the  substance,  as  shown. 


Name . 


Date 


Substance  No. 


EXPERIMENTS. 

RESULTS. 

INFERENCES. 

I. 

Add  drops  of  H  Cl. 

No  precipitate  made. 

Absence  of  Group  I.    Ag, 

11. 

Hg  (ous),  Pb. 

To  I.  add  H2S. 

No  precipitate  made. 

Absence    of    Group    II. 

Hg(ic),  Bi,  Cu,  Cd,  As, 

Sb.Sn. 

III. 

To   the  original    solution 

No  precipitate  made. 

Absence    of    Group    III. 

addNH4ClandNH4OH. 

Fe,  Al,  Cr. 

IV. 

To  1  1  1.  add(NH4)aS. 

No  precipitate  made. 

Absence  of    Group    IV. 

V. 

Mn,  Zn,  Ni,  Co. 

To   original  solution    add 

A  white  precipitate. 

Presence    of    Group    V. 

NH4Cland(NH4)2  CO3. 

Ba,  Sr,  or  Ca. 

VI. 

To   the    original    solution 

No    precipitate   made 

Absence  of  Ba. 

add  solution  of  Ca  S  O4. 

in  the  cold. 

VII. 

Heat  VI.  to  boiling. 

A  white  precipitate. 

Presence  of  Sr. 

VIII. 

Flame  test. 

Brilliant  crimson. 

Confirms  presence  of  Sr. 

Hence  substance  No. 


is  a  compound  of  strontium, 


V.     ANALYSIS   OF   A   COMPLEX   SUBSTANCE. 

A  substance  which  contains  more  than  one  metal  or  salt 
may  be  analyzed  by  a  skillful  use  of  the  foregoing  facts. 
If,  for  example,  you  have  a  mixture  of  silver  nitrate  and 


136        LABORATORY  STUDIES  IN  CHEMISTRY. 

copper  nitrate,  you  can  separate  the  two  metals,  and  then 
identify  each;  for,  if  you  add  HC1  to  the  solution  of  the 
mixture,  you  will  convert  the  Ag  into  white  insoluble  AgCl, 
while  the  copper  compound  will  stay  in  solution.  If,  then, 
you  filter  the  mixture,  you  will  have  the  silver  in  the  pre- 
cipitate on  the  filter,  and  the  copper  in  the  filtrate.  You 
can  prove  the  white  precipitate  to  be  silver  chloride,  and 
thus  prove  that  Ag  was  present  in  the  original  substance ; 
and  you  can  also  identify  Cu  in  the  filtrate,  and  thus  prove 
that  this  metal  was  also  present  in  the  original  substance. 

Thus,  "  separations  "  of  the  metals  belonging  to  different 
groups  can  be  made  by  the  use  of  the  group  reagents  H  Cl, 
H2  S,  and  so  on,  in  their  proper  order,  and  then  the  metals 
in  each  group  may  be  identified. 

But  the  full  directions  for  such  advanced  work  would 
better  be  obtained  from  the  instructor,  or  found  in  works 
devoted  to  Qualitative  Analysis. 


APPENDIX. 


A.   The  Names,  Symbols,  and  Approximate  Atomic  Masses 
(Atomic  Weights)  of  the  Elements. 


NAMES. 

Symbols. 

Atomic 
Masses. 

NAMES. 

Symbols. 

Atomic 
Masses. 

Aluminum  .  .  . 

Al. 

cy. 

27 
120 

Molybdenum    , 
Nickel  . 

Mo. 

Ni. 

96 

58.5 

As 

75 

Nitrogen  .... 

N. 

14 

Ba 

137 

Osmium  .... 

Os. 

191 

Beryllium1  .  .  . 
Bismuth     .... 

Be. 
Bi. 
B 

9 
207 
11 

Oxygen    .... 
Palladium  .  .  . 
Phosphorus   .  . 

0. 
Pd. 
P. 

16 
106 
31 

Br 

80 

Platinum    .  .  . 

Pt. 

194 

Cadmium  .... 

Cd. 

Cs 

112 
133 

Potassium  .  .  . 
Rhodium     .  .  . 

K. 

Rh. 

39 
104 

Calcium  

Ca 

40 

Rubidium  .  .  . 

Rb. 

85 

Carbon    

C 

12 

Ruthenium   .  . 

Ru. 

103.5 

Cerium   .      ... 

Ce 

141 

Samarium  .  .  . 

Sm. 

150 

Chlorine    .... 
Chromium   .  .  . 
Cobalt 

01. 
Cr. 
Co 

35.5 
52 
59 

Scandium   .  .  . 
Selenium    .  .  . 
Silicon  

Sc. 
Se. 
Si. 

44 
79 
28 

Cb 

94 

Silver    

Aff. 

108 

Copper    

Cu. 

63.3 

Sodium    .... 

Na. 

23 

Didymium   .  .  . 
Erbium      .... 

Di. 
Er 

142 

166 

Strontium  .  .  . 
Sulphur    .... 

Sr. 

s. 

87.3 
32 

Fluorine    .... 
Gallium  . 

F. 
Ga 

19 
70 

Tantalum   .  .  . 
Tellurium  .  .  . 

Ta. 
Te. 

182 
125 

Germanium    .  . 
Gold 

Gr. 
Au 

73 
196.7 

Terbium  .... 
Thallium    .  .  . 

Tb. 
Tl. 

148 
204 

Hydrogen  .... 

H. 
In 

1 
'  113  4 

Thorium  .... 
Tin            .... 

Th. 

Sn. 

232 
118 

Iodine  

I. 

127 

Titanium    .  .  . 

Ti. 

48 

Iridium  

Ir. 

193 

Tungsten3  .  .  . 

W. 

184 

Iron  

Fe. 

56 

Uranium  .... 

U. 

240 

Lanthanum  .  .  . 
Lead  

La. 
Pb. 

138.5 
207 

Vanadium  .  .  . 
Ytterbium  .  .  . 

V. 
Yb. 

51.2 
173 

Lithium  

Li 

7 

Yttrium    .... 

Yt. 

89 

Mff 

24 

Zinc                .  . 

Zn. 

65 

Manganese  .  .  . 
Mercury 

Mn. 
H>. 

55 
200 

Zirconium  .  .  . 

Zr. 

90 

1  Beryllium  is  also  called  glucinum,  with  the  symbol  Gl. 

2  Columbium  is  also  called  niobium,  with  the  symbol  Nb. 

3  Tungsten  has  also  been  culled  Wolframium. 

137 


138  APPENDIX. 


B.    The  Metric  Measures,  -with  their  Equivalent 
English  Values. 

1.    MEASURES  OF  LENGTH. 

The  standard  unit  is  the  meter,  —  the  length,  at  0°  C.,  of  a  certain 
bar  of  platinum  preserved  in  the  Archives,  Paris. 

1  millimeter  (mm.)  =      0.03937  inch. 
10  millimeters    =  1  centimeter  (cm.)    =      0.3937       " 
10  centimeters  =  1  decimeter  (dm.)     =      3.9371  inches. 
10  decimeters    =  1  METER  (m.)  =    39.3707       " 

10  meters  =  1  decameter  (dcm.)  =    32.81      feet. 

10  decameters    =  1  hectometer  (hm.)  =  109.30       yards. 
10  hectometers  =  1  kilometer  (km.)     =      0.6214  mile. 

1  meter  =  3.2809  feet  =  1.0936  yards. 

1  inch     =  2.534    centimeters.     1  foot     =•  30.479  centimeters. 

1  yard     =  0.9144  meter.  1  mile    =  1.6093  kilometers. 

2.    MEASURES  OF  VOLUME  OR  CAPACITY. 

The  unit  is  the  liter,  —  the  volume  of  pure  water  which  at  4°  C. 
would  just  fill  a  cubical  vessel,  each  of  whose  sides  is  one  deci- 
meter in  length. 

1  cubic  centimeter  (cc.)  =  1  milliliter    =  0.06103  cubic  inch. 
10  cc.    =  10  milliliters  =  1  centiliter   =  0.6103        "       " 
100  cc.    =  10  centiliters  =  1  deciliter     =  6.1027    cubic  inches. 
1000  cc.    =  10  deciliters    =  1  LITER  (1.)  =  1.0567  U.  S.  quarts. 

0.9469  liters  =  1  U.  S.  liq.  quart  =    57.752  cubic  inches. 
3.785     liters  =  1  U.  S.  gallon        =231 
4.544    liters  =  1  Imp.  gallon         =  277.27 

29.57  cubic  centimeters  =  1  U.  S.  fluid  ounce  =  iV  U.  S.  pint. 
28.4  cubic  centimeters  =  1  Imp.  fluid  ounce  =  •£••$  Imp.  pint. 
16.386  cubic  centimeters  =  1  cubic  inch  =  0.554  U.  S.  quart. 

3.     MEASURES  OF  MASS  OR  RELATIVE  WEIGHT. 

The  standard  unit  is  the  kilogram,  —  the  mass  of  a  certain  block 
of  platinum  preserved  in  the  Archives,  Paris.  The  smaller  unit,  one 
gram,  is  the  weight  of  one  cubic  centimeter  of  pure  water  at  4°C. 


APPENDIX.  139 

1  milligram  (mg.)  =      0.0154       grain. 
10  milligrams    =  1  centigram  (eg.)   =      0.1543 
10  centigrams   =  1  decigram  (dg.)     =      1.5432       grains. 
10  decigrams     —  1  GRAM  (g.)  =    15.4323 

10  grams  =  1  decagram  (dcg.)  =  154.323  " 

10  decagrams    =  1  hectogram  (hg.)  =      3.527     ozs.  Avoir. 
10  hectograms  =  1  kilogram  (kg.)     =      2.2046  Ibs.  Avoir. 

0.4535  kilograms  =  1  Ib.  Avoir.     28.349  grams  =  1  oz.  Avoir. 

0.3872  kilograms  =  1  Ib.  Troy.      31.103  grams  =  1  oz.  Troy. 

4.    MEASURES  OF  TEMPERATURE. 

Freezing  point  of  water  =      0°  Centigrade  (C.)  or   32°  Fahrenheit  (F). 
Boiling  point  of  water  =  100°  "  or  212°          " 

lo  c.  =  |°  or  1.8°  F.  1°  F.  =  f°  or  0.555°  C. 

To  change  a  Centigrade  temperature  to  its  equivalent  Fahrenheit 
temperature,  multiply  by  §-,  and  add  32°  to  the  product. 

To  change  a  Fahrenheit  temperature  to  its  equivalent  Centigrade 
temperature,  subtract  32,  and  multiply  the  remainder  by  f . 


C.    Apparatus  and  Chemicals. 

1.   THE  APPARATUS. 

The  following  list  includes  all  the  apparatus  required  for  the 
experimental  course  described  in  this  book.  The  set  has  been 
arranged  with  special  reference  to  the  needs  of  beginners,  and  to  the 
wants  of  teachers  who  are  oftentimes  so  pressed  by  other  duties 
that  little  time  is  left  for  the  preparation  and  oversight  of  labo- 
ratory work. 

Many  of  these  articles,  once  obtained,  should  last  a  long  time; 
many  others  are  more  likely  to  perish,  and  should  be  bought  in 
larger  number  than  that  prefixed  to  them  in  the  list,  which  indi- 
cates the  outfit  for  a  single  table.  Further  suggestions  on  this  point 
may  be  found  in  the  notes  which  follow  the  list. 

1  Balance. 

BEAKERS,  Griffin's  low,  wide,  with  lip:  — 

2  No.  00,  capacity  1£  ounces. 
1         "      0,         "        2*       " 

1        "     1,         "        5         «* 


140  APPENDIX. 

1  Blowpipe,  jeweler's,  brass,  10  inches. 
BOTTLES,  wide-mouthed,  flint  glass,  round :  — 

2  Capacity  4  ounces. 
2  6       " 

2  "        8       " 

1  Bunsen  burner,  with  regulator  for  air. 

2  Burettes,  Mohr's,  with  tip  for  pinchcock. 

1  Ch!oride-of-calcium  tube  (drying  tube)  1  bulb,  6  inches. 

1  Cobalt  glass,  plate  2X3  inches. 

1  Cork  borers,  set  of  3,  for  holes,  ^2^  _p       4    inch. 

1  File,  triangular,  5  inches. 
FLASKS:  — 

4      Erlenmeyer  form  (conical),  Bohemian  glass,  ring-neck,  diame- 
ter of  mouth  1  inch,  capacity  10  ounces. 

1      Round-bottom,  ring-neck,  diameter  of  mouth  f  inch,  capacity 
8  ounces. 

1      Side-neck,  tube  set  high,  capacity  5  ounces,  diameter  of  mouth 
£  inch. 

1      Side-neck,  tube  set  high,  capacity  8  ounces,  diameter  of  mouth 
|  inch. 

1  Forceps  (pincers),  steel,  plain,  \\  inches. 

1  Funnel,  best  German,  60°,  stem  pointed,  diameter  2|  inches. 

1  Funnel  tube,  thistle  top,  10  inches. 

2  Glass  stirrers  (rods),  one  end  rounded,  8  inches. 

1  pound  glass  tubing,  best  German,  ^\  inch  outside  diameter. 
1  Graduated  cylinder,  on  foot,  25cc.  with  lip. 

1  Mortar,  of  German  porcelain,  deep  form,  with  pestle,  diameter 

3^  inches. 

2  Pinchcocks,  Mohr's,  medium  size,  strong  spring. 

1  Platinum  foil,  medium  thick,  for  blowpiping,  \\  inches  square. 

1  Platinum  wire,  No.  26,  3  inches. 

PORCELAIN  DISHES,  Ptoyal  Berlin,  glazed  inside  and  outside:  — 

2  No.  00,  diameter  2J  inches. 
1         "      0,         "         3       " 

1  "  3,  "  3|  " 
1  Retort  stand,  iron,  3  rings. 
1  Retort-stand  clamp,  Bunsen's  small  universal,  with  fastener. 

RUBBER  STOPPERS,  best  soft  rubber:  — 
4      With  2  holes,  selected  to  fit  the  conical  flasks. 

1  "     1  hole,          "         "         "     round-bottom  flask. 

2  "     1  hole,          "         "         "     side-neck  flasks. 


APPENDIX.  141 

2  Solid,  selected  to  fit  the  side-neck  flasks. 

1      Solid,        "         "      "       side-neck  ignition  tube. 

3  feet  rubber  tubing,  white,  best  quality,  usual  thickness,  fa  inch 

in  diameter  inside. 
Rubber   tubing,  for  the   Bunsen   burner,  ^  inch   inside,  white, 

double  thickness.     (Length  depends  on  the  position  of  the 

gas  fixture.) 

1  Spatula,  horn,  5  inches. 
(5  Test  tubes,  6  X  £  inches. 

1  Test  tube  with  side  neck,  hard  glass,  for  ignition,  6  x  f  inches. 
1  Test-tube  brush,  brass-wire  handle. 
1  Test-tube  rack  for  6  tubes. 

1  Thermometer,  chemical,  scale  C.°  on  stem,  to  200°. 
1  Water  pan,  agate  ware,  flat  bottom,  about  10  X  4  inches. 
1  Weights,  20  g.  to  1  mg.  in  case. 

Notes. 

1.  It  will  not  be  necessary  to  provide  all  the  articles  in  this  com- 
plete set  for  every  member  of  a  class.     One  balance  and   set  of 
weights,  one  thermometer,  two  or  three  pieces  of  platinum  foil,  one 
graduated  cylinder,  two  burettes,  and  one  set  of  cork  borers,  may 
suffice  for  a  class  of  ten  to  twenty  students  if  necessary. 

2.  Owing  to  the  fragile  and  perishable  character  of  some  articles, 
they  should  be  purchased  in  larger  numbers  than   the  above  list 
would  indicate.     Such,  for  example,  as  test  tubes,  flasks,  beakers, 
and  porcelain  dishes,  should  be  bought  by  the  dozen  or  gross,  and 
always  more  than  sufficient  to  supply  the  students  in  the  outset. 
Rubber  tubing  should  be  bought  by  "the  piece,"  which  is  12  feet. 

3.  A  balance  sensitive  to  1  mg.  inclosed  in  a  glass  case  is  desira- 
ble.    One  which  is  sensitive  to  1  eg.  is  less  costly,  and  fairly  satis- 
factory for  all   the  work   described.     With  only  a  pair  of  "  hand 
scales,"  costing  much  less  than  the  balance,  very  good  work  can 
be  done. 

4.  For  some  pieces  of  the  apparatus,   cheap  substitutes  may  be 
found  among  articles  of  familiar  use  in  the  household.     Such  sub- 
stitution should  be  made  only  by  compulsion.     Students  in  chemistry 
are  as  much  entitled  to  know  what  chemical  apparatus  is,  as  they 
are  to  know  what  chemical  methods  and  principles  are.     It  is  better 
to  obtain  apparatus  from  reliable  dealers  who  will  supply  it  from 
the  same  stock  from  which  they  supply  chemists.     If,  in  our  list, 
any  exceptions  to  this  are  warranted,  they  may  be  found  in  the 


142  APPENDIX. 

test-tube  rack,  which  can  be  made  in  good  style  by  any  carpenter 
who  consults  Fig.  2,  p.  12,  and  the  test-tube  brush,  for  which  a 
rod  of  wood,  with  a  piece  of  sponge  wired  upon  the  end,  is  a  good 
equivalent. 

5.  Before  purchasing  the  apparatus,  its  cost  can  be  learned  by 
sending  the  list  to  a  dealer  in  chemical  supplies,  who  will  return  a 
statement  of  his  prices. 

2.    THE  CHEMICALS. 

In  the  following  list  are  included  the  names  and  formulas  of  all 
the  chemicals  required  for  the  course  of  studies  laid  down  in  this 
book.  These  substances  should  be  of  the  best  quality.  Many  should 
be  "C.  P.;"  i.e.,  chemically  pure.  It  is  well  to  buy  chemicals  as 
you  should  buy  apparatus,  from  well-known  dealers  in  laboratory 
supplies. 

Reagents,  which  are  to  be  used  by  students,  should  be  kept  upon 
their  tables  in  small  bottles:  liquids  in  glass-stoppered  bottles  holding 
about  125  cc.  (or  four  oz.),  and  solids  in  salt-mouth  bottles  holding 
2  oz.  If  substances  are  to  be  used  by  the  teacher  or  are  to  remain  in 
stock,  they  may,  for  the  most  part,  be  kept  in  the  bottles  in  which 
they  are  bought.  Every  bottle  should  be  distinctly  and  permanently 
labelled. 

Unless  economy  must  be  rigidly  practiced,  the  supply  will  not  be 
limited  to  the  substances  in  this  list.  Specimens,  in  great  variety, 
are  very  desirable. 

Acetic  acid,  pure H  C2  H3  O2. 

Alcohol C2H6O. 

Alum K2A12(S04)4  +  24H20. 

Ammonium  carbonate,  C.  P (NH4)2  CO3. 

Ammonium  chloride,  C.  P NH4  Cl. 

Ammonium  hydroxide NH4  OH. 

Ammonium  nitrate,  cryst NH4  NO3. 

Ammonium  sulphate (NH4)2SO4, 

Animal  charcoal,  or  boneblack .     .     .     .  C. 

Antimony  chloride,  sol.  C.  P SbCl3. 

Arsenious  oxide As2  O3. 

Barium  chloride,  C.  P Ba  C12. 

Barium  nitrate,  C.  P Ba  (NO3)2. 

Bismuth  nitrate,  cryst.  C.  P Bi(NO3)3. 

Cadmium  chloride Cd  C12. 

Calcium  chloride,  cryst.  C.  P Ca  C12. 


APPENDIX.  143 

Calcium  chloride,  granulated. 

Calcium  oxide  (quicklime) Ca  O. 

Calcium  sulphate,  calcin Ca  SO4. 

Chrome  alum K2  Cr2  (SO4)4  +  24  H2  O. 

Cobalt  sulphate Co  SO4. 

Cochineal. 

Copper  filings,  or  clippings. 

Copper  wire,  No.  24  and  No.  16     ...  Cu. 

Copper  chloride Cu  Clg. 

Copper  oxide Cu  O. 

Copper  sulphate,  C.  P CuSO4. 

Corks,  best  velvet,  diam.  small  end,  1,  ^f , 
|,  f,  |  inch,  by  the  dozen. 

Ferrous  chloride Fe  C12. 

Ferric  chloride Fe2  Clg. 

Ferrous  sulphate,  pure Fe  SO4. 

Ferrous  sulphide,  sticks -.  Fe  S. 

Filter  paper,  best  German,  white,  sheets  19  X 19  inches. 

Hydrochloric  acid,  pure H  Cl. 

Iron  filings,  coarse. 
Iron  wire,  No.  24. 

Lead  acetate Pb  (C2  H3  O2)2. 

Lead  nitrate Pb  (NO3)2. 

Litmus,  cubes. 

Logwood,  chips  or  extract. 

Magnesium  ribbon Mg. 

Magnesium  chloride,  cryst MgCl2. 

Magnesium  sulphate,  C.  P MgSO4. 

Manganous  chloride Mn  C12. 

Manganese  dioxide,  powder      ....  Mn  O2. 

Manganous  sulphate MnSO4. 

Marble Ca  CO3  (impure). 

Mercury,  redistilled Hg. 

Mercuric  chloride Hg  C12. 

Mercuric  oxide Hg  O. 

Nickel  sulphate Ni  SO4. 

Nitric  acid H  NO3. 

Phosphorus P. 

Potassium K. 

Potassium  bromide,  C.  P KBr. 

Potassium  carbonate,  C.  P K2CO8. 


144  APPENDIX. 

Potassium  chlorate K  Cl  O3. 

Potassium  chromate K2  Cr  O4. 

Potassium  cyanide K  Cy. 

Potassium  dichromate K2  Cr2  O7. 

Potassium  ferrocyanide K4  Fe  Cy6. 

Potassium  hydroxide,  pure K  O  H. 

Potassium  iodide KI. 

Potassium  manganate K2  Mn  O4. 

Potassium  nitrate,  cryst KNO3. 

Potassium  permanganate K2  Mn2  O8. 

Potassium  sulphate,  cryst K2  S  O4. 

Silver  nitrate,  cryst Ag  N  O3. 

Sodium Na. 

Sodium  biborate  (borax) Na2B4O7  +  10H2O. 

Sodium  bromide Na  Br. 

Sodium  bicarbonate H  Na  C  O3. 

Sodium  carbonate,  C.  P Na2  C  O3. 

Sodium  chloride  (common  salt)      .     .     .  Na  Cl. 

Sodium  hydroxide,  C.  P Na  O  H. 

Sodium  nitrate Na  N  O3. 

Sodium  sulphate Na2SO4. 

Sodium  sulphite Na2SO3. 

Strontium  chloride SrCl2. 

Strontium  nitrate,  C.  P Sr  (NO3)2. 

Sulphuric  acid,  pure H2  S  O4. 

Sulphur,  flowers S. 

Sulphur,  roll S. 

Tin,  granulated Sn. 

Zinc,  sheet,  common Zn. 

Zinc,  granulated Zn. 

Charcoal,  common C. 

Starch,  common C6  H10  O6. 

Sugar,  granulated,  common C12  H22  On. 


14  DAY  USE 

RETURN  TO  DESK  FROM  WHICH  BORROWED 

LOAN  DEPT. 

This  book  is  due  on  the  last  date  stamped  below,  or 

on  the  date  to  which  renewed. 
Renewed  books  are  subject  to  immediate  recall. 


LIBRARY  USE 

OQT151960 

Rex*  D  ETD 

AOT  4  r* 

OCT  1?  1960 

LD  21A-50m-4,'60 
(A9562slO)476B 


General  Library 

University  of  California 

Berkeley 


YB   16859 


3  61 7 


